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140 Cards in this Set
- Front
- Back
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Part One: From Retina to Cortex
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Projection from slides - cornea - lens - retina (first neural struc) - neurons send axons to Lat. Geniculate body - projections from synapse and axons sent along optic radiations - primary visual cortex.
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Visible Light within the electromagnetic spectrum
(purple to red) |
Human visible spectrum: 400 -700 nm wavelength; after uv and before infrared. Bees have UV rays visible but no organism has much beyond 1/2 through UV and infrared visible. Evolved close to star w/ light in our spectrum.
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Gross Anatomy of the Eye
1) Cornea 2) Anterior Chamber and Aqueous Humor 3) Vitreous Humor |
1) Cornea (Outermoust, some light refraction/bending)
2) Anterior Chamber (with clear liquid - Aqueous humor - lens further bends light - primary mechanism to focus, aka accomodation. 3) Exits lens through gelatinous Vitreous Humor. |
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Gross Anatomy of the Eye
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4) Retina/back of eye: thin sheet of neural tissue. 5) Sclera: hard, white, outer coating. 6) Optic disk and then the optic nerve in the opening in back of sclera for nerves to exit.
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The Retina via opthalmoscope
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Yellow circle: Optic DISK. Optic nerve where bv enter/exit eye. Fovea in center: A little darker b/c of larger density of cells in center; thicker bv by outside of eye vs middle; avoid fovea to avoid blockage/absorbing light. Evolution to see as much light as possible. Nothing to receive light (photoreceptors) - blind spot (That is the position of your optic disk with respect to your fovea).
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How the Lens Works
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Focusing (far away): ciliary muscle contracts-fatter; cm att. to lens and moves right. Shaped like a circle around lens. Opening of cililary muscle smaller and pressure released on zonule fibers. Measures of iris separate from ciliary muscles reponsible for accomodation. *Cil Not directly connec to lens and are circular. Contracting relaxes lens. Muscles of iris are sep from cm. Focusing (accommodation) on
near OR far objects requires some contraction of the ciliary muscle, and that this contraction causes the lens to become more rounded or convex. In general, the shorter the distance, the more accommodation is needed to focus an object. |
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Refractive Errors
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Emmetropia: Parallel rays are focused exactly on the retina and vision is perfect. Myopia: focused before getting to the back of the retina (or longer eyeball). Hyperopia: focused behind retina/later.
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Light enters eye via cornea to lens to vitreous humor to photocep (gather info, change in mem poten.) Then to cell #2:___ and #3____. **Horiz and Amacrine cells interact btwn cells.
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2) Bipolar cells (send info to #3 retinal ganglion cells/RGCs). Photoreceptors are in the back of the eye (inside-out organization vs other animals). Change in membrane receptors. Axons of RGCs are fibers of optic nerve which project info to thalamus/LGN. See diagram.
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Photoreceptors: Rods
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Rods:
Highly sensitive to light Only one kind of photopigment (Rhodopsin) “Bleached” under daylight conditions Active in total darkness to moonlight Absent at the Fovea (therefore must look beside stars) |
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Photoreceptors: Cones
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Relatively insensitive to light
Three kinds—provide for color vision Active in indoor lighting to daylight conditions Highest density (almost exclusively) in Fovea |
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Organization of the Fovea
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Foveola: best chance for detecting light; little overlying tissue over photoreceptors. No bv -> avascular zone. Most highly sensitive to light during day.
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Photoreceptor Density Distributions
(Max acuity at center of retina) |
Zero degrees: back of eye. Rods most prevalent in periphery (temporal and nasal) from fovea. Cones become very small when closely packed at zero degrees. (No photorec in optic disk). Cones at fovea for looking directly at an object.
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Receptive Fields in the Eye
*Rec. field in periphery is Larger than in the fovea. |
Periphery: higher degree of convergence per ganglion cell. Ratio may be 30:1 (photoreceptors for single ganglion cell) vs fovea (1:1 ratio; G. cell receives info from one photoreceptor. Action potentials: know which photorec is responsible vs in periphery w/ poorer visual acuity. Receptive field is related to number of photoreceptors. (Larger in periphery).
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Transduction and Transmission of Visual Information
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Light always from ganglion cell direction. Only photoreceptors detect light. Change light energy into form for detection.
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Transduction and Transmission of Visual Information
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1) Hyperpolarizing: (ongoing current -> dark current/present in dark until lighted) Shut off -> hyperpol in mem. 2) Depol of bipolar cell (disinhibition vs from dark current inhibiting). Ca influx. Vesicles of NT fuse...rel -> to post syn cleft/membranes of G cells. Detect NT, causing action poten. 3) Depol of ganglion cell. Fires action potentials.
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Receptive Field
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A cell’s receptive field is that portion of the visual world that drives the response of that cell.
A cell’s receptive field is the part of visual space to which the cell responds. A cell will only respond to stimuli presented in its receptive field. Rec. Field for photorec; for ganglion cell; for cortical cells, etc. As eye moves, visual world moves. |
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The Advanced Retinal Circuit
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Light through axons&bodies of RGCs, cell bodies of Amacrine cells, Bipolar, Horiz to rods/cones. Amacrine: crosstalk/lat processing among photo rec and bipolar cells. H: among bipolar and RGCs. Immediate processing before reachign back of eye.
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Center-Surround Organization of the Receptive Field
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H&A interact w/ signal coming from photorec and bipolar cells, therefore a cell's rec field includes all photorec. Only cells in middle will cause RGC to fire. Photo rec on outside of rec field ->inhibition of action poten on RGC (Not fire if light on surround b/c H are depol and bipolar in middle are inhibited) (Inhib reac btwn H&Bipolar on surround.)If light on center photorec, excited bipolar, inhib bipolar outside, inc firing RGCs.
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Lateral Inhibition
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Interac btwn cells. Ex. Light on center, Photoreceptors Hyperpolarize, Bipolar cells Depol, the connected Horiz cell is excited and leads to Hyperpolarization in Bipolar cell of surrounding portion. Therefore the Gang. cells fire in center and inhibit firing in surround. (Lateral inhibition: mediated by H and A cells.) Lattice: higher convergence in periphery. Rec field competing usu lateral inhib.
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Effects of Lateral Processing
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Lattice and grey dots. Mach Bands (Receptive fields competing for lat. inhibition. Enhancement. some cells' rec fields entirely w/in one bar. Other cells overlap in rec fields. (ex. half dark, half light leads to 'lighter' message.)
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Receptive Field Organization
On-Center vs Off-center RGC |
(On-Center RGC) Light on specific ret. ganglion cell w/ center of recp field. Inc firing rate. Light on periphery of rec field, due to lat inhib, will Dec firing rate. Removed light from surround will then rebound and fire at light offset. Released initiated lat inhibition with light on surround.
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Receptive Field Organization of Retinal Ganglion Cells in eye. . .1) On-center GRC (receptive field):
1) b. off-surround of that RGC since it is on-center |
Partial reason for Mach bands effect.
1) Increased action potentials when light shown here. 1) b. Dec firing rate when light shined here. |
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1) Off-center with on-surround
2) Onset of light stimulus has |
1) Dec firing rate vs inc action poten in surrounding. 2) Highest firing rate at first. On-center: firing rate decreases. *Weaker during entire T1 and none during T2 when light entirely removed.
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1) Off-center ganglion cell:
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1) Abolishment of action poten and then hidden response (light shown on center but then off response - excitation has rebound effect) Same effect but if only in surrounding portion. Light in center, then offset light inc action poten. B/c: disinhibition of cell. (+ vs - inhib) Rebound effect, aka off response.
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1) Dark spot in center - only surrounding has light. Mostly inhibited.
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1) Dec in action poten.
2) Off-center: No light in central/inhib - inc action poten firing. [Dark spot removed - excitation. Short burst - a lot for on-center gc, one for off-center] |
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Video of Cat lgn (received projections from rgcs; single cell in lateral gen nuc)
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On-cell. Recordings of nerve cells; hear action potentials whether bar of light or circle, etc.
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Receptive Field Structure
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When light is shown in on-center of rec field, photorec hyperpol (fig b), dec nt release onto bipolar cells. Two types of bipolar cells based on kinds of Glu rec: class using AMPA (excitatory) and one mGlur (inhib)
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mGlur receptor bipolar cell connected to:
AMPA rec connected to: (Dark center: 2) |
1) oncenter 2)off-center RGCs. So, light shown in center-hyperpol-two diff responses in bipolar cells. ON: DEPOL/Disinhib. - excit leads to inc NT rel OFF: Hyperpol/inhib - dec NT rel and inhib in off-center ganglion cell. (Dark center: hyperpol in on-center.)
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Dark Center (always NT rel - dark current - until light shown...)
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Light, then shuts of Glu release. On-center bipolar cell gets NT in dark from photorec. mGlur is inhib. Once light shines, Glu rel shuts off - disinhib. Inc in mem poten. Inc nt rel into synapse and rgcs (excit synpase, so firing rate inc)
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Dark: AMPA
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In dark, off-center cell uses ampa. Usually excited in dark. Light* on center-glu rel turned off; mem poten dec - hyperpol. Not usual excitation as in dark. Bipolar cell dec Glu rel onto ganglion cell; fires less.
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Summary
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On-center bipolar cell /w light in center = off-center w/ light in surround.
AMPA always off-center: Light on center therefore does not fire but on w/ dark center (surrounding relatively lighter), inc mem poten. |
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On-Center ganglion cells are inhibited maximally: 1)
2) B) Rec field moves across edge - light only on some surrounding (inhib) portion. C) Halfway into light |
1) When there is light only on surround portion. 2) B) firing rate dec. C) Inhib RGC firing but also excited center - Net result no change.
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D) Mostly in light. E) All in light.
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D) Firing rate inc a lot. Not fully inhibited - the surround* E) Some dec, not maximal inc (center wins slightly over surround, E does not equal A) Slight advantage to center even though surrounding inhibits.
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Mach Bands
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Not one rgc but rec fields that are adjacent are completely in dark, some in transition, etc.
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Optic Chiasm
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{Sent axons through optic disk to first cranial nerve -optic nerve) Greek for X. Optic Nerve projects back to a structure from both eyes - optic chiasm.
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Projections at optic chiasm decide which half of brain to go to. Split:
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50/50 in humans; temporal half of eye project to ipselateral/same side LGN/as eye. (Nasal/medial hems project axons that cross contralat LGN) Each LGN receives info from both eyes. Left LGN receives info from nasal half of right eye and temporal half of left eye. LGN - where axons terminate also project to Superior Colliculus is the major brain struc for animals w/ no visual cortex.
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Pathway from RGCs:
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Once the info gets from the RGCs (these send axons through optic disk) - thalamus - to the LGN within the thalamus, then cells within project along optical radiations to optical occipital lobe -striate cortex (Primary Visual Cortex)
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The Lateral Geniculate Nucleus
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Has 6 layers in primates (3 in cats). Info stays seg even though from both eyes - eye specifc per layer. (Diag - coronal sec) Layers 1-6, contralat in blue 1,4,6 and ipselat 2,3,5. Eye specific orientation remains through striate cortex staying seg. Spatial organization of inputs. Therefore:
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Retinotopic Organization
(Lower visual field -> superior to calcarine fissure) |
Visual fields overlap. 1/2 of what left eye sees is also seen by 1/2 of right. Primary visual cortex corresponds to halves. Divided in half horiz as well - superior portion of left visual field to inferior portion of cortex. Calcarine sulcus divides lower and upper visual fields. More peripheral/outward vs center/back (mapped on brain).
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Function of Visual Cortex
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David Hubel and Thorsten Wiesel
Recorded action potentials in Visual Cortex Nobel Prize. |
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Receptive fields in Visual Cortex
1) Primary Visual Cortex (simple cell) |
1) Elongated rec field; direction matters. Inc firing rate when off. Angle of bar of light matters. Huge square covering entire rec. field: no response. (Off response if just inhib portion covered...)
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Primary Visual Cortex (complex cell)
3) Hypercomplex cell |
3) Rec field in center; angle matters, otherwise no response. Dark bar resulting in firing.
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Visual cortex cell:
2) Bar across all three centers |
One visual cortex cell receives input from many RGCs/LGN cells and therefore angle matters or all three on-centers would not be activated. If only in one center - dec in action potentials as seen in simple cells. Angled bar would not excited enough LGN centers. [LGN cells like next to eachother b/c of retinotopic map which project to visual cortex. If to same vc cell, it would have same rec field as sum of those lgn rec fields.]
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Columnar Organization of Orientation Selectivity in Primary Visual Cortex.
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- Difficult to get same angle. Particular angle varied across cortical surface. But, down perp - same angle rec field organizations. Grouped in columns. Coded for similar angles if adjacent.
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Specialized Visual Functions
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What else does the visual system do?
Color Vision We’ll cover retinal mechanisms Also cortical mechanisms for complex tasks Object Recognition Spatial Localization |
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Red and Green make
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Yellow? Retinal ganglion cells have a color-opponent center-surround organization that forms the basis for color vision. Yellow on, blue off and vice versa. Red on, green off and vice versa.
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Retinal Basis for Color Vision
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At the level of the rgc the three-color code is translated itno an opponent-color system. The retina contains two kinds of color-sensitive ganglion cells: red-green and yellow-blue.
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Opponent-Processing and Color Vision
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[Ex. red light stimulates red cone-> excites red-green ganglion cell, signals red. If yellow light signals red and green equally, no signal change]
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Higher-order Visual Cortex
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More complex visual tasks
More than 20 separate visual cortical areas in primates for processing visual stimuli |
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Visual Association Areas
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Most of the outputs of the striate cortex/V1 are sent to area V2 before converging. The visual assoc cortex contains two streams of analy: the dorsal [WHAT] and ventral [WHERE] streams.
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Visual Association Areas
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(Magnocellular sys is in all mammals. Parvocellular and koniocellular only in primates. Receive info from diff types of ganglion cells. P&K receive info about wavelength from cones-hence color. P: high spatial resolution and low temporal resolution (detailed but slow) Magno: color-blind but movement sensitive)
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Object Recognition
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In primates, object identification takes place in the inferior temporal cortex
Responses of cells in this area are “tuned” for complex objects Faces, fire extinguishers, stuffed animals Responses of cells in this area to simple objects (lines, circles) are quite poor |
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Object Recognition:
inferior temporal cortex |
Here analyses of form and color are put together and 3D objects and backgrounds are achieved. Responds best to 3D objects even when partially occluded.
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Disorders in perception
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Visual agnosia
Deficit in vision that is not due to blindness Results from damage to brain structures Apperceptive visual agnosia Inability to recognize certain objects Prosopagnosia Lesion to a part of the inferotemporal cortex leads to an inability to identify faces Person knows that the object is a face, but cannot recognize whose face |
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Disorders of movement perception
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Akinetopsia
Inability to perceive movement Caused by damage to medial superior temporal cortex (MST or V5) |
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The Traveling Sound Wave
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Compressed air and rarefied air, alternating. Normale human sensitivity range 20 - 20,000 hz. Infants have higher ranges.
Patterns go down ear cannal to ear drum. |
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Dimensions of Sound
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Physical Dimension correlated with Perceptual dimension. Loud vs soft (high vs low amplitude) Frequency (how many compressions and rarefications are there in a given length; pitch diff) low: slower compressions/long period, high: faster/closer periods)
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Dimensions of Sound
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Complexity (Perceived as timbre)(simple/smooth/pure vs complex/richer/subfreq) Complexity indicates what instrument for each not even if freq/pitch and amplitude are the same.
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Ear
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Pinna: fleshy, external part. Funnels sound to drum and to localize (ex. fold ears: ineffective at localizing sound)
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Tympanic Membrane
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Aka. Ear drum. Compression and rarefication of air impinges on tympanic mem. Thin, flexible, sensitive, vibrates in synchrony w/ sound. Attached to: Ossciles (Malleus, Incus, Stapes: hammer, anvel, stirrup) Bones of middle ear. Hammer connects to ear drum and anvel. Incus connects to stapes situated in cochlea.
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Oval window
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Where stapes impinges on cochlea is an oval window (thin portion of cochlea wall). When moves - moves fluid inside cochlea (liquids difficult to compress) Round window -> fluids to be let out; opening in cochlea wall.
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Three bones turn air energy...
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Into physical movement of liquid vs of bone. Tympanic mem has limits - info lost. Converting energy is ineff - 99.9% lost b/c diff mediums. (Air-phys/mechanical energy - liquid medium). Ossicle arrangement produce countering effect - amplify signal (mechanical advantage)
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Eustachian tube
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Connects to throat. Keeps air pressure on ends of tym mem equalized. Rupturing could happen. Ex. having a cold. Eustachian tube fills w/ fluid. More difficult for sound to vibrate through unless press equalized.
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Signals out of cochlea travel out...
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Through 8th Cranial Nerve (info about balance and from cochlea, hearing. aka vestibular cochlea nerve). (Auditory Nerve portion)
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Cochlear Anatomy
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Cross section. Scala Vestibuli & tympani below -> fluid filled spaces. Scala media btwn (no fluid) ->specialized struc giving off axons to auditory nerve. Organ of corti (scala media struc) -> takes vibrations in fluid in cochlea into nerve impulses projected to brain.
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Hair Cells
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Cilia sticking out of cells touch against tectorial mem (elongation of mem encasing cochlea fluid in scala vestibuli; over hair cells). Vibrated by vibration of fluid by stirrup. Moves tect. mem causing cilia to move. These fire action poten. down 8th cranial nerve -> inner hair cells have no direct contact w/ tect mem. Otherwise same func as outer hair cells.
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Action of the Cilia
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Recordings of displaced tips towards shortest hair cells -> few action poten. Opposite direc->inc in action poten.
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Cation channel on each cilia...
[Neurons can fire max of 500 hz for a short per; 300-500 per sec.] |
Thread/tip link connects to next shortest cilia. Shorten tip link->close cation ch. At rest- somewhat open. Pull on string->open cation ch (Ca and K+ enters into hair cell -> depol hair cells -> action poten down auditory nerve. Maximal displacement in this directon results in maximal firing. In the direction of tallest cilia.
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Tonotopic Organization
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Map based on freq/tone of stimulus. Scala v&t have same fluid actually when unrolled. Basilar mem in middle.
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Tonotopic Organization
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Basilar mem: stiffness is diff along length -> more flexible at apex vs base. Low freq sounds will move easier vibrating at apex. More vibrating at apex. High freq-> more displaced at base. [Low freq=apex=flexible vs. high=base=stiffer]
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Tonotopic Organization
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Map out maximal displacement. W/out round window, fluid could not move. Serves as equal and opposite to stapes actions. Bulges to absorb energy. Even if low hz, if at certain part of cochlea, indicates high/low frequency: Placecode theory.
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Tonotopic Organization
“Place Code” |
The freqency of the stimulus is coded by the particular location of maximal activation in the cochlea
(Hair cells living at a particular point corresponds to a particular freq of sound; indep of action poten; infer freq of stimulus) Used majority of time. |
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Vibrational Synchrony
“Rate Code” |
Hair Cells can fire action potentials in synchrony with the original sound vibrations
Especially for low frequency sound Restricted to low freq vs place code. |
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Central Auditory Pathways
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Dorsal and Ventral Cochlear nuclei (hair cells project here). Hair cells synapse w/ neurons projecting to Sup Olivary Nuc. Hair cells from right ear/right cochlea proj to right side of brain stem to ipselat & contralat super olivary nuc from right side for ex. Sup Olivary Nuc receives info from both ears.
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Superior Olivary Nucleus
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Sound localization (reaching one ear/closest first). Sup Olivary Nuclei on both hemis. Then project to: Inferior Colliculus - sound. [Sup Collic receives info about sight] To Thalamus: medial geniculate body [lgb from visual sys]. To Primary Auditory area of cerebral cortex in temporal lobe, ventral to lat fissure.
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Auditory Cortex
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Primary Auditory Cortex is in Temporal lobe. (See secondary auditory cortex below and posterior speech cortex adjacent) Cells lined up in order: high freq towards caudal end/base of cochlea and low freq cells at anterior/rostral/apex portion of cortex.
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Higher-order auditory cortex
Josef P. Rauschecker Two streams of information |
Dorsal
“where” pathway Localization of sound source Ventral “what” pathway Identification of sound source identity |
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Disorders of Sound Perception
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Lesions of auditory association areas can bring about auditory agnosias
Right hemisphere damage leads to an inability to understand the meaning or source of sounds Left hemisphere lesions usually leads to some form of speech perception disorder Wernicke’s Aphasia—can’t understand what is being said; speech is fluent but meaningless |
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Higher-order Auditory Function: Disorders of Sound Perception.
Rt vs lt hemis damage. |
Lesions of auditory association areas can bring about auditory agnosias (lack of knowledge; can hear but not identify; not disorder of sensation but percep)
Right hemisphere damage leads to an inability to understand the meaning or source of sounds Left hemisphere lesions usually leads to some form of speech perception disorder |
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Biological Mechanisms of Language
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Requirements for the use of Language and Speech:
Symbolic representations: Words Rules for using symbols: Grammar Ordering symbols: Syntax Giving appropriate emotional valence: Prosody |
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Structures involved in producing and understanding speech
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Broca's Area: sup to lateral fissure.
Wernicke's Area: further caudal (see diag) Primary Auditory Cortex: hear sounds first necessarily. Primary somatic sensory cortex (sensation of speaking, position of tongue) Primary visual cortex (facial expressions) |
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Speech Disorders
1) Agrammatism 2) Anomia |
Agrammatism
Difficulty understanding or properly using word endings, verb tense, and word order. Ex. not knowing x did this to y (order) of saying and picture. Could make logical deductions. Anomia Difficulty finding the right word to describe an object, action or attribute. Circuitous routes to convey words; could discern from tone that a ques was asked. |
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3) Aphasia
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Difficulty producing or comprehending speech
not produced by deafness or a simple motor deficit caused by brain damage Common side effect of strokes. If chronic degeneration may be permenant. |
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Paul Broca
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French Neurologist
First Patient “Tan” (M. Laborgne) Could only say tan. Hole in left hemis. (Func spec came recently) Broca performed an autopsy of the brain upon Tan’s death “On parle avec l’hemisphere au gauche” Unscientific. |
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Carl Wernicke
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German Neurologist
Studied many patients with speech disorders Published precise descriptions of speech-related areas in the temporal lobe Studied the brains of dozens of patients |
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Broca’s and Wernicke’s Aphasias
(Now have 8-10 subtypes) |
Broca: Aka: motor, expressive, or production aphasia.
Halting vs fluent speech. Tendency to repeat phrases or words (preseveration). Disordered syntax, grammer, struc of words. Comprehension intact. |
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Wernicke’s Aphasias
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Aka sensory or receptive aphasia. Fluent speech, little spontaneous repetition, syntax and grammar adequate. Contrived or inappropriate words, comprehension not intact.
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Language: Hemispheric Lateralization
(But writing w/ left hand is done by right hemis; speech -left; plasticity when removed early in life; both ears project sounds to both sides of brain) |
(Usu via epileptic/corpus callosum severed patients) Would not know what was seen if object presented in left visual field b/c both eyes see it, travels to rt visual cortex, but cannot get to left. Or, right visual field object, seen w/ both eyes into left visual cortex to broca's area also in left hemis.
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Speech production and recognition
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Comes in PAC (primary auditory cortex) to BAC to Wern. Area to Post Lang Area (bundle of audit. assoc cortex; many connec to resst of brain). Questions integrated w/ percep and memories. From post. lang. area to Broca's area (connec w/ motor cortex)
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Language Representation Variability
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See slide.
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Somatosensation
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The cutaneous senses respond to several different types of stimuli: pressure, vibration, heating, cooling, tissue damage
Some receptors report changes in muscle length to the brain; kinesthesia Additional receptors provide information about the internal organs (e.g., gastrointestinal system) |
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Cutaneous Receptors
Hairy Skin |
) Free Nerve Endings - Painful stimuli and associated with hair
2) Ruffini - Responds to indentation of skin 3) Pacinian - Responds to rapid vibration |
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Glabrous Skin -- more complex
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1) Pacinian - high freq. vibration
2) Meissner’s - low freq. vibration 3) Merkel’s - indentation of skin 4) Free Nerve Endings - Pain and associated with complex structures 5) Ruffini - indentation of skin |
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Cutaneous Receptors
Functional Principles |
Adaptation
decreased responding with repeated stimulation fast and slow adaptation |
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Central Somatosensory Pathways
Dermatomes |
See diagram.
Cervical vert, thoracic, lumbar, sacral... |
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Chapter 5.
Excitotoxic lesions: |
A more selective method of producing brain lesions w/ the excit. am. acide kainic acid killing neurons by stimulating them to death. Injected through a cannula destroying cell bodies in vicinity but not axons of diff. nearby neurons. Determines whether beh. effect due to destroyed axons nearby instead.
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Stereotaxic surgery (Solid arrangement surgery)
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Ability to locate objects in space. Uses a stereotaxic apparatus (which contains a holder that fixes the animal's head in a standard position and a carrier that moves an electrode or cannula measured distances in all three axes of space using stereotaxic atlas.
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Fixative
2) Microtome |
A chemical such as formalin; used to prepare and preserve body tissue. 2) Instrument producing very thin slices of body tissues.
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Cell-body stain
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Methylene blue stained cell bodies of brain tissue; Nissl substance takes up the dye and consists of RNA, DNA, and assoc proteins located in nucleus and scattered in cytoplasm. Stain is Not selective for neural cell bodies and includes Glia.
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Scanning electron microscope
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Less magnific than standard transmission electron microscope transmitting the elctron beam through tissue. Shows objects in 3D with a moving beam of electrons.
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Anterograde labeling method
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A histological method labeling axns and terminals; employ chemicals taken up by dendrites or cell bodies and are then transported through the axons toward the terminals.
Anterograde tracer: Pha-L |
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PHA-L
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A protein derived from kidney beans and used as an antereograde tracer; taken up by dendrites and cell bodies and carried to the ends of the axons. An immunocytochemical method makes these modlecules visible.
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Immunocytochemical methods
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Take advantage of the immune reac. The body's immune sys has the ability to produce antibodies in response to antigens.
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Retrograde labeling method
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A histological method that labels cell bodies that give rise to the terminals that form synapses w/ cells in a particular region. Det. afferent connections; moving backward b/c chemicals are taken up by terminals and back to cell bodies.
[Ret-Aff-Backward-Labels cell bodies via terminals] |
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Flourogold
2) Pseudorabies virus |
A dye serving as a retrograde label; taken up by terminals and carried back to cell bodies.
2) Weakened form of pig herpes virus used in transneuronal tracing, which labels a series of neurons that are interconnected. |
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Computerized Tomography
(location of lesion) |
CT scan; employs a computer to analyze data obtained by a scanning beam of x-rays to produce a 2d picture of a slice through the body. Ex. Location of a tumor.
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Magnetic resonance imaging
(location of lesion) |
No x-rays; extremely strong magnetic field through the patient's head; the nuclei of some atoms spin w/ a particular orientation. If a radio freq wave is then passed through the body, the nuclei emit their own radio waves at diff freq. The MRI scanner is tuned to detect the radiation from hydrogen atoms; can also be taken in the sagittal or frontal planes.
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Goal to destroy or inactivate specific brain region
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1) Radio freq lesion (destroys all brain tissue near tip of electrode) 2) Excitotoxic lesion (spares axons passing through region) 3) Infusion of local anesthetic or musimol (temporarily inactivates specific brain region; animal can serve as its own control)
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Microelectrode vs macroelectrode
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Very fine tip to record activity of indiv neurons. This technique is usu called single-unit recording. 2) Records activity of a large number of neurons in a particular region in brain.
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Electroencephalograms (EEGs)
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An electrical brain potential recorded by placing electrodes in the scalp.
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Magnetoencephalography
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Performed w/ neuromagnetometers, devices that contain an array of several SQUIDS, oriented so that a computer can examine their output and calculate the source of partic signals in brain. Detects groups of synchronously activated neurons by means of the magnetic field.
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2-DG
2) Autoradiography |
1) A sugar that enters cells along with glucose but is not metabolized. 2) Locates radioactive substances in a slice of tissue; the radiation exposes a photographic emulsion or a piece of film covering the tissue. The molecules of radioactive 2-DG appear as silver grains after radioactivity.
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Fos
2) Positron Emission Tomography (PET) |
A protein produced in the nucleus of a neuron in a response to synaptic stimulation. 2) The use of a device that reveals the localization of a radioactive tracer in a living brain. Patient receives 2-DG; expensive; short half-lives of chemicals; trained personnel.
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fMRI
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1)Higher resolution of PET scans and faster, more detained. Permits the measurement of regional metabolism in the brain.
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Microdialysis
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A procedure for analyzing chemicals present in the interstitial fluid through a small piece of tubing made of semipermeable membraine that is implanted in the brain.
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Chemical stimulation
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Usu via excit. amino acids injected into vrain vs wire. Disadvantage: slightly more complicated, requires cannulas, tubes, pumps, syringes, am. acid solutions. But does not activate axons; more localized.
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Transcranial magnetic stimulation (TMS)
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Uses a coil of 8-shaped wires to stimulate neurons in cerebral cortex. Placed on top of skull; pulses of electricity send magnetic fields that activate neurons in the cortex. The effects are very similar to those of direct stimulation. Used to treat depression. Interferes w/ functions of stimulated brain region.
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Transcranial magnetic stimulation
2) Immunocytochemical |
A coil fo wires shaped like a number 8 is placed on the head of a person about to undergo. 2) To identify neurons producing a particular peptide.
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1) Labeling method to trace pathways followed by efferent axons. A histological emthod that labels the axons and terminals of neurons whose cell bodies are located in particular region.
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1) Anterograde vs. Retrograde. (Labels cell bodies that give rise to terminals that form synapses with cells in a particular region.)
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1) The first step in visual perception occurs when light:
2) Protanopia: 3) When low frew info ins removed from an image, it becomes: |
1) Causes a photopigment to split into its two constituents. 2) Usu male. 3) More difficult to identify.
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1) The extrastriate cortex
2) Neurons in the V4 of extrastriate cortex: 3) Achromatopsia: |
1) Consists of several regions that each respond to a particular kind of visual info. 2) Respond to a variety of wavelengthsof light. 3) Lost some/all color vision.
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1) Inferior temporal cortex:
2) Prosopagnosia 3) Neurons in area V5 |
1) Analyzes form and color. 2) Do not recognize faces. [A region of the extrastriate cortex located at the base of the brain; involved in perception of faces and other complex objections requiring expertise - fusiform face area) 3) Respond to movement.
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1) Dorsolateral MST (MSTd) appears tobe: 2) Ganglion cell 3) Ventral stream
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1) the analysis of optic flow. 2) Receives visual information from bipolar cells; its axons give rise to the optic nerve. 3) A sys ofinterconnected regions of visual cortex involved in the perception of form.
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1) Simple cell 2) Bipolar cell 3) Connects adjacent photoreceptors and outer processes of the bipolar cells.
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1) An orientation sensitive neuron in the striate cortex whose receptive field is organized in an opponent fashion. 2) Located in the middle layer of the retina, conveying info from the photoreceptors of ganglion cells. 3) Horizontal cell.
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Cutaneous Receptors.
Eipidermis (outer, stratifed, top-dying cells) and Dermis (where sensory organs are located) 1) Free nerve endings |
1) In hairy and glabrous skin. Pseudounipolar cells; one end of axons to dermis and one through brain. Often assoc/wraps around hair (vs. Meissner's or sweat glands) Carry info about painful stimuli.
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2) Ruffini Corpuscles
[*All struc are specialized nerve endings (not nec free nerve endings); not sep. cells converging on other nerves.] 3)Pacinian corpuscles |
2) Specialized nerve endings in upper layer of dermis. Respond to indentation. Look diff from Merkel's. 3) Respond to rapid vibration/rough surfaces. Lower layers of dermis. (Glabrous skin has two types: Pacinian and Meissner's for lower freq virbrations/even rougher surfaces.
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Central Somatosensory Pathways
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1) Dorsal root ganglion (cell body collection; pseudounipolar cells - These bifurcate to sensory receptors and other end to brain) End not going to sensory rec: 2) First way to get to brain: Precise touch, kinesthesia send axons through dorsal columns of spinal cord -> brainstem -> cross side of brain through medial lemniscus -> Ventral posterior nucleus of thalamus -> Primary somatosensory cortex (Carried on ipse/same side)
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2nd) Pain/Temp
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*Spinothalamic tract. 1) Cross to other side of spinal cord at the level of dorsal root ganglion 2) Up spinal tract; medulla 3) Medial lemniscus (midbrain) 4) ventral posterior nucleus of thalamus 5) Primary somsatosensory cortex (Carried on contralateral sides)
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Dermatomes
(an area of skin that is supplied by a single pair of dorsal roots) (8,12,5,5) |
Each vert section w/in each vert has a particular set of dorsal root ganglion; comes out at every space at each level to carry these fibers. Cervical: Neck, dorsal half of arm and hand.
Thoracic: Trunk Lumbar: Front of leg Sacral: Back of leg, genital. |
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Organization of Primary Somatosensory Cortex
(Arranged orderly) |
Primary somatosensory cortex (S1) divided in half by central fissure. First stop [like for visual sys; visual bars of light and the second cortex processes the object].
SII: much smaller, caudal/posterior/further back. Interprets info from cutaneous rec in some part. |
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Olfaction
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Chemical senses (taste and smell) may be the earliest sensory systems to develop (chordates arose w/in sea and needed to detect chemical concen of food vs danger) Stimuli for odor (odorants) consist of volatile, lipid-sol, organic substances having a molecular weight of approximately 15 to 300
(dogs are closer to the ground/odor and therefore have more developed smell) |
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Olfaction
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Almost all odorous compounds are lipid soluble and of organic origin
Individual receptor cells in the nasal epithelium will respond to many dozens of odors (*vs tectorial mem for particular freq photorec -> narrow wavelength for response) **Cannot predict odor from receptor firing. |
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Olfaction
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Much more complex task to detect odor molecules and what stimulus is and means. (20,000 shades of color w/ 3 rec types -> nec to have specific tuning vs 20,000 chem compounds in olfactory w/ necesary to detect wide differences in molecular structure.) There are 350 (humans) to 1000 (mouse) diff olf. rec (for diff qualities of chemical stimuli) vs about 3 for visual sys.
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Elements of Olfactory Processing
((There are 350 to 1000 different olfactory receptors! Not one rec for each odor)) |
Odor binds to olfac. receptor protein on surface of rec neuron. Axon projects to olfac bulb in brain (similar to role of thalamus for visual sys). Projects to Mitral/tufted cells. Relayed to olfactory cortex.
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Midsagittal diagram
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Olfac. epithelium lines nasal cavity. Has olfactory rec. neurons projecting axons to olfactory bulb (above and medial to eyes; ventral brain). Cribiform plate (bones)
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Receptor Neuron Projections
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Zones (IV total) of olfactory epithelium correspond with olfactory bulb.
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See diagram w/ Olfactory tract, optic chiasm, olfactory tubercle, pyriform cortex, amygdala, and entorhinal cortex.
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Amygdala and entorhinal cortex: different information such as motor planning and emotional states as well. Reason why olfac. sys is good at evoking emotional memories.
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Taste
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Five tastes: Sweet, Salty, Bitter, Sour, “Umami” (book doesn’t count umami; MSG)
NO EVIDENCE for spatially segregated organization of taste on the tongue |
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Taste diag
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Papilla on surface of tongue. Taste buds, receptors, and afferent axons.
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See diag:
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Ventral posterior medial nucleus of thalamus. Nucleus of solitary tract. Tongue, larynx. Also, axons from nucleus of solitary tract to v.p.m.n. of thalamus gustatory cortex.
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