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84 Cards in this Set
- Front
- Back
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Define the Limbic System
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- comprised of both cortical and subcortical structures located mainly in the medial and ventral regions of the cerebral hemisphere
- play important role in behavior and memory |
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What did they think the original Limbic Structures were?
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- forms ring around diencephalon (limbus)
- cingulate gyrus - parahippocampal gyrus |
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Cats and Sham Rage Experiment
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Cats that had their caudal hypothalamus lesioned would experience aggressive/fearful behaviors (hiss & arch back) - it was thought that the hypothalamus was important in regulating emotion
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Papez Circuit
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Information comes into the neocortex - cingulate cortex - hippocampus - fornix - hypothalamus for emotional expression - anterior nuclei of thalamus for motor response - cingulate cortex for emotion experience/perception - neocortex for emotional coloring (attach emotion to these sensory experiences)
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Limbic System Theory
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hippocampus is more related to memory function (main function is to tie certain memories to emotions)
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Limbic Structures
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- hypothalamus - affector of emotion
- Thalamus (AN, MD) - hippocampus - memory function - Amygdala - emotional responses (fear/aggression) - Basal Forebrain - (basal nucleus of meynert) - increase attention and awareness that helps with memory - Septal Area - Nucleus Accumbens - pleasure center |
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Structure that is Important for Emotion (fear/aggression)
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Amygdala on temporal lobe
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Kluver-Bucy Syndrome
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- temporal lobectomy in rhesus monkeys affects behavior
- causes a decrease in fear and aggression - similar to human lesions of the temporal lobe |
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Certain Characteristics Associated with Kluver-Bucy Syndrome
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- absence of fear (placidity)
- hyperphagia - overeats or attempts to eat inappropriate food/objects that are not food - hypersexuality - mount any and everything! (in humans it takes the form of suggestive behavior and talk) - visual agnosia - objects are not recognized visually and objects are examined orally and by touch |
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Parts of the Amygdala
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- collection of nuclei in the anteromedial temporal lobe at the anterior end of hippocampus
- basolateral - largest in humans and major connections to cortex, BF, and medial thalamus - centromedial - connections to olfactory bulb and cortex - central - connections to hypothalamus and brainstem for autonomic functions |
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Amygdala: Cortical Input/Output
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- comprised of the hippocampal formation - connecting memory to emotion
- comprised of uncinate fasciculus - function is unknown but connects limbic structures with orbital frontal lobes |
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Amygdala: Subcortical Input/Output
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- bidirectional but these structures play a major role in output (efferent in nature)
- important in motivational, autonomic, and neuroendocrine aspects TWO PATHWAYS: - stria terminalis - leaves amygdala, proceeds caudally and follows the contours of stria terminalis/fornix, sends projections to hypothalamus and to septal area - function includes olfactory information, appetite regulation, or detecting odor - ventral amygdalfugal pathway - shortcut to hypothalamus and spetal area, set of projections that leave the amygdala and directly proceeds to the brainstem or to the forebrain structures - forebrain pathways are important in emotion, motivation, and cognitive functions - brainstem pathways are important in regulating ANS/homeostatic functions |
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Amygdala: Olfactory Connections
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- connections project directly to the olfactory bulb and to the cortex
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Amygdala and Studies of Responses to Tones
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Rats presented with good and bad tone, would receive shock to foot when bad tone was present. When amygdala was lesioned they would no longer have physiological responses to bad tone
*tone comes into auditory cortex: - basolateral nuclei and goes to cerebral cortex for emotional experience - central nuclei and goes to hypothalamus for autonomic response or to brainstem for behavioral reaction |
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Predatory Aggression
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- attacks made against members of a different species to obtain food
- few vocalizations |
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Affective Aggression
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- threatening or defensive posture
- vocalizations - high levels of ANS activity |
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Pathway for Aggression
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comes into amygdala and relayed to hypothalamus (medial areas for affective while lateral areas for predatory aggression) then goes to motor/visceral components for a response to be produced
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Bitemporal Lobotomies in Alpha Monkeys
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reduces member to bottom of hierarchy
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Electrical Stimulation of Amygdala Causes:
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agitation and affective aggression
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Definitions of Immediate Memory, Working Memory, Long-term Memory
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- immediate - fractions of a second or seconds, awareness of the sensory experience, involves attention and awareness of ascending reticular activating system is involved
- working - seconds to minutes, memories held briefly in mind that enable a goal to be accomplished (i.e. looking for a pair of keys and know where you' ve looked) - long-term memory - days to years, memories that are more established that require medial structures of the brain |
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Damage to Medial Structures and Cerebral Cortex
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Medial Structures - STM
Cerebral Cortex - LTM |
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Hebb's Cell Assembly
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sensory experience causes groups of neurons to fire that are interlinked with reciprocals to each other, the conection between these cells become very efficient and strong (neurons that fire together, wire together), the neurons are hardwired in the brain and if they are exposed to similar stimuli then you activate those cells that are wired to sensory receptors and form a memory
*how much the weight of the connection between two units should be increased or decreased in proportion to the product of their activation |
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Definitions of Amnesia, Limited Amnesia, Dissociated Amnesia
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Amnesia - lost of memories that are already there or inability to learn (caused by concussion, chronic alcoholism, encephalitis, brain tumor, or stroke)
- limited amnesia - most common, due to injection/trauma of the thead and normally will see other cognitive defects - dissociated amnesia - people who come back from war may have this amnesia, no other cognitive deficits present (rare) |
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Definitions of Retrograde, Anterograde, Transient Global Amnesia
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- retrograde - memory loss of events before the trauma
- anterograde - inability to form new memories - transient - sudden onset of anterograde often accompanied by retrograde, permanent memory gap |
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Learning
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acquisition of new information and knowledge
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Two Types of Memory
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- retention of learned information
- declarative memory (explicit) - facts and events, can be consciously recalled but easily forgotten - nondeclarative memory (implicit) - procedural memory that involves skills/habits, cannot be consciously recalled, requires repitition and practice but less likely to be forgotten |
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Anatomy of Declarative Memory Formation: Pathway
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Medial Temporal Lobe
- hippocampus - parahippocampal gyrus Diencephalic Area - mediodorsal and anterior thalamic nuclei - mammillary bodies PW cortical association areas - parahippocampus and rhinal cortical areas - hippocampus - fornix - thalamus/hypothalamus |
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Effects of Bilateral Medial Temporal Lobectomy (cortex, amygdala, & anterior 2/3 of hippocampus)
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- perception, personality, & intelligence normal
- partial retrograde amnesia - extreme anterograde amnesia |
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Medial Temporal Lobes and PW Memory Processing
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- hippocampus
Parahippocampual gyrus makes up the : - entorhinal cortex - input/output relay between association cortex and the hippocampal formation - perirhinal cortex - parahippocampal cortex |
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Input and Output From Hippocampus
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- input - arrives at the hippocampus through the parahippocampal, entorhinal (this is the main input station though), and perirhinal cortexes via frontal, paraieto-occipital, and temporal association cortexes
- output - hippocampus to diencephalic and septal nuclei via fornix |
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What structures are important for consolidation of memory?
Where are the memories stored? |
Memory is consolidated in medial temporal structures
Memory is stored in once Papez Circuit has run its cycle and continues to the cortex (association areas) for easy reactivation |
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Damage to Dorsomedial Thalamic Nucleus/Anterior Thalamic Nucleus
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- cognition normal
- partial retrograde amnesia - severe anterograde amnesia - proves that diencephalic structures and medial temporal are important for memory consolidation |
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Korsakoff Syndrome
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- psychosis characterized by confusion, a loss of recent memory and often a tendency to fabricate accounts of recent events (due to damage to diencephalic and frontal lobe structures)
- most often the result of chronic alcoholism/nutritional deficiencies (vitamin B) which leads to lesions of dorsomedial thalamus/mammillary bodies - retrograde amnesia is more severe |
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Where is the storage of long-term declarative memory?
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cerebral cortex
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Short-term Memory Storage
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hippocampus
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Explicit Memories of Storage: Attention, Working Memory, Consolidation
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- attention - brainstem/dienchephalon
- working memory - frontal association cortex - consolidation - medial temporal cortex |
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Alzheimer's Disease
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- affects 4-5 million Americans
- increases with age (1% <65 to 40% >85) - 50% of all cases of dimentia |
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Early Symptoms of AD
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- forgetfulness and memor loss
- disorientation Final Stages - incapable of slef care - incontinent - bedridden |
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Pathophysiology of AD
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- formation of amyloid plaques due to A-beta protein
- neurofibrillary tangle due to tauo proteins - neurodegeneration - common in medial temporal lobes, basotemporal cortex, parieto-occipital cortex, posterior cingulate gyrus, frontal lobes, nucleus basalis (projects acetylcholine cells to cortex), septal area |
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Genes Linked to AD
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- Amyloid Precursor Protein - precursor to forming amyloid plaques
- Trisomy 21- common in pts with Down Syndrome - Presenillins - involved in processing and cleaving APP, defects lead to increase in AD - Apo E - apo E allele 2 decreases your risk but if you have apo E allele 4 the it increases your risk |
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Consciousness
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person is awake and aware of himself or herself and the surroundings
involves 2 main parts: - reticular formation is responsible for alert/attention - cerebral cortex is necessary for state of awareness |
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Different Stages of Consciousness
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Lethargy - slowed speech and voluntary movement are diminished and slow
Stupor - will speak only if pain is present, voluntary movements are nearly absent, eyes are closed and very little spontaneous eye movement or will not speak if in deep stupor Coma - (unconscious) unarousable/unresponsive which the patient lies with the eyes closed, will respond reflexively to painful stimuli, will not speak |
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Alterations of Consciousness Brought on By Lesions to:
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- cerebral cortex (has to be bilateral)
- thalamus - brainstem *often the result of concussion/contusion/intracranial pressure such as a hemorrhage or tumor |
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Persistent Vegetative State
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- RF is intact but cortex is non-functioning
- person is awake/eyes open - no awareness and cannot respond to stimuli such as verbal command/pain - usually seen in severe head injuries or anoxic cerebral conscious - possible to have wakefulness without awareness but not possible to have awareness without wakefulness |
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Definition of Sleep
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- changed state of consciousness but not unconscious
- decreased activity of RF and thalamocortical activating system - active or passive |
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Attention: Selective and Sustained
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- selective - attention to certain objects, stimuli, or concepts to the exclusion of others
- sustained - concentration, vigilance, nondistractibility |
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Example of Selective and Sustained Attention
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Student studying for a final exam during a frat party
Reading and focusing on text and content and ignoring music and noise around her is example of selective attention Continuing to read “boring” Neuroscience notes while fun is happening around her and ignoring pleas of other students to join in fun is an example of sustained attention |
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Anatomy of Attention
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- Widespread projection systems
- Frontal and parietal association cortex - Limbic cortex and structures - Tectum and pretectal area and pulvinar - Other structures i.e. cerebellum, BG - Nondominant hemisphere plays a more important role in attention than dominant |
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Attention Deficit Hyperactivity Disorder: 3 Characteristics
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- inattention
- hyperactivity - impulsiveness/impatient |
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Cause of ADHD
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- MRI studies show prefrontal cortex and BG smaller
- abnormal genes related to dopamine function |
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Statistics of ADHD
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- 5-10% of school aged children
- 3-5x more common in boys then girls - 15-20% of patients continue to have ADHD into adulthood |
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Treatment o ADHD
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- behavioral therapy
- CNS stimulants that enhance dopaminergic transmission * Ritalin and Concerta - block DA reuptake *Adderall increases presynaptic release of DA |
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Definition of Seizures
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- transient appearance of inappropriate, synchronous, high frequency firing of a large number of neurons in the cerebral cortex
- a sx of abnormal brain function and can occur in individual who do not have epilepsy *ictal - during a seizure *post-ictal - immediately after a seizure *interictal - between seizures |
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Definition of Epilepsy
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- a disorder in which there is a tendency to have recurrent or unprovoked seizures
- affects 1% of the population |
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Partial Seizures
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- partial (focal or local) - initiated in a small, local part of the brain
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Classification of Partial Seizures
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- simple - consciousness spared, 5-10 seconds, no new post-ictal deficits, auras are common
- complex - impairment of consiousness, 30 seconds-1 to 2 minutes, common in temporal lobe, post-ictal deficits present |
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General Seizures
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- involve the entire brain
- called tonic-clonic (grand mal) |
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Classification of General Seizures
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- tonic phase (10-15 seconds) - patient loses consciousness and contraction of all muscles
- clonic phase (30 seconds to 2 minutes) - rhythmic symmetrical muscle jerking, incontinence and tongue-biting, massive ictal sx of tachycardia, HTN, hypersalivation, dilation and then immediate post-ictal where the patient is immobil and flaccid that can last minutes to hours |
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General Seizure
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- involves the entire brain
- absence (petit mal) |
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Classification of Petit Mal
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- brief episodes of staring and unresponsiveness lasting 10 seconds or less
- loss of awareness without loss of muscle tone - no post-ictal deficits - most often in childhoold and can occur multiple time per day - can be provoked by hyper ventilation, strobe lights, or sleep deprivation |
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Risk of New Onset of Seizures
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- high in infancy and childhood
- declines in adulthood - rises again in the elderly |
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Name of Seizures in Childhood
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Febrile Seizures
- simple - brief tonic-clonic seizures; not associated with increased risk of epilepsy - complex - lasting more than 15 minutes or occurring more than once in 24 hours and have focal features; could indicate increased risk for epilepsy |
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Causes of Seizures in Elderly
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- cerebral vascular disease
- brain tumor - neurodegenerative disorders |
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Drug Therapy for Epilepsy
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- useful for 2/3-3/4 of patients
- enhance function of GABA by partially blocking excitatory transmission - side effects include sleepiness, dizziness, blurry vision, cognitive impairment, GI upset |
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Mental Retardation
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disruption of brain development resulting in subaverage cognitivie functioning that impairs social adaptive behavior
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Standard IQ Test for MR
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- 100 is the average
- <70 is considered MR |
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Causes of MR
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- Trisomy 21
- Phenylketonuria |
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Trisomy 21
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- most common autosomal chromosome abnormality
- 1 in 800 babies - decreased frontal lobes |
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Phenylketonuria
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- metabolic disorder (autonomic recessive disease) resulting in accumulation of phenylalanine
- results in demyelination and neuronal loss - can be prevented if low PDU diet with 30 days of birth - tested with heel stick and placed on low PKU diet |
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Other Causes of MR
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- accidents during pregnancy
- poor nutrition - impoverished environment |
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Dementia
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- generalized mental deterioration but usually applied to gradually progressive disorders
- memory loss and los of at least one other cognitive function |
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Common Causes of Dementia
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- AD (#1)
- Vascular Dementia (#2) - Thymine Deficiency due to alcoholism - intracranial neoplasm - head injury |
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Some Forms of Dementia are Reversible:
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- hyperthyroidism
- vitamin deficiency - depression - tumors |
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Dyslexia
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- developmental reading and writing disorder
- deficits with phonology - taught decoding skills - abnormalities in parieto-temporal cortex |
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Statistics of Dyslexia
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- accounts for 80% of learning disorders
- 5-10% among school aged children |
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Concussion
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- mild head trauma that results in reversible impairment within minutes to hours following head injury
- CT & MRI are normal |
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Severe Head Trauma Can Cause Permanent Damage Due To:
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- diffuse axonal injury
- intracranial hemorrhages - cerebral contusion - cerebral edema |
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How Do People Sustain a Head Trauma?
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- adults - MVA (15-24 at highest risk)
- older adults - due to falls - infants - accidental falls & Shaken Baby Syndrome |
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Most Commonly Injured Parts of the Brain Due to Head Trauma
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orbitofrontal, anterior, and inferior temporal regions
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Sx of Severe Head Trauma
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- cognitive dysfunction
- personality changes |
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Treatment for Severe Head Trauma
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- Diuretics (decrease swelling)
- Anti-seizure medications - Coma-inducing (brain needs less oxygen) - Hypothermia therapy (decreases cellular metabolism) - Therapy (occupational, speech, physical)- focused on regaining lost skills |
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Tumors
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- abnormal growth of tissue that forms a mass
- diagnosed with MRI & CT - Glioblastoma most commonly seen |
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Sx of Tumors
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- headaches
- seizures - altered mental function - dizzy |
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Treatment of Tumors
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- surgery
- radiation - chemotherapy - immunotherapy |
