learning, memory & consciousness
dissociative identity disorder
- (multiple personality disorder) - shifts in consciousness and behavior suggesting distinct personalities - 90-95% report childhood abuse - may be a mechanism to cope with stress (provide escape and, often, the opportunity to engage in prohibited forms of behavior) - physiological measures support this interpretation; alters respond differently in skin conductance, EEG, visual event-related potentials, and cardiovascular measures - brain scans show reduced activity in the orbitofrontal cortex, along with increases in the other frontal areas and differences in activation between alters while listening to personally relevant traumatic material - hippocampus increases & decreases activity when switching btw alters
neurofibrillary tangles
- Abnormal accumulations of the protein tau that develop inside neurons and are associated with the death of brain cells in people with Alzheimer's disease and Down syndrome.
down syndrome
- Also have plaques & tangles & they invariably develop alzheimer's if the live to the age of 50 - Caused by an extra chromosome 21 & they found a mutation in the amyloid precursor protein (APP) gene
hippocampus, CA1
- CA1: primary output from hippocampus - damage of CA1 results in moderate anterograde amnesia & minimal retrograde amnesia
confabulation
- Fabricate stores & facts to make up for those missing from their memories - Associated w/ korsakoff's syndrome - "Creative remembering" - Occurs following damage to specific area in the frontal lobes - Due to inability to distinguish btw current reality & earlier memories
retrieval
- accessing the consolidated memory - glutamate required for retrieval - blocking glutamate receptors prevents retrieval - prefrontal area: directs search strategy for retrieval in hippocampus
amyloid plaque protein
- accumulate near terminal buttons and interfere with neural transmission - causes memory and failure to form long-term memories in mice - only moderately related to cognitive impairment. - ADDL, a soluble form of amyloid, seems more likely - ADDL causes memory and LTP failure in mice. - ADDL is 70% higher in the brains of Alzheimer's patients. - Clumps of amyloid, a type of protein, that cluster among axon terminals and interfere with neural transmission in the brains of people with Alzheimer's disease and Down syndrome.
temporal lobe
- alzheimer's: global loss of neurons in temporal lobes - Structures of the medial temporal lobe are important in learning - Hippocampal formation forms part of the medial temporal lobe - Patients w/ varying degrees of temporal lobe damage have helped determine which structures are involved in amnesia & in memory - Lesions from Alzheimer's are located in the temporal lobes; b/c of their location, they effectively isolate the hippocampus from its inputs & outputs which partly explains the early memory loss - Disrupted communication btw the primary visual area & the visual association areas in the parietal & temporal lobes explains the visual deficits that plague some alzheimer's sufferers
attention
- attention is necessary for consciousness, although attention (without working memory) is not sufficient - how the brain allocates limited resources to focus on some neural inputs while excluding others. - physiological process -- changes in attention matched with changes in neural activity -- thalamus is a critical region -- also requires working memory and other brain areas - Anterior cingulate cortex may play an executive role - dorsal network: allocates attention under goal directed control - ventral network: responds to stimulus demands
body image
- contributes to a sense of self because we have an identification with our body and with its parts; it is our body, our hand, our leg - importance of body image to the sense of self is the phantom limb phenomenon - because the body image is part of the equipment we are born with, it becomes an important part of the self—even when it conflicts with reality. - body image is a phenomenon that develops primarily in adjacent parietal areas - damage to the inferior parietal area can also cause the most extreme of body image illusions, the out-of-body experience - body image resides primarily in parietal areas
mirror neurons
- critical to developing that ability to attribute mental states to others - they give mirror neurons considerable credit for social understanding, empathy, and the ability to understand the intentions of others - malfunction in the mirror neuron system is one reason suggested for the autistic individual's failure to develop a distinction between self and others, along with empathy and theory of mind - Justin Williams and his associates suggest that the problem is not in the mirror neurons themselves, but in the regulation of their function by the anterior cingulate cortex
water maze
- disabling hippocampus causes impaired learning in water maze - (A) water maze task apparatus in which rats use spatial cues (represented by colored shapes) to learn and remember the location of a stationary escape platform (red circle) hidden beneath the surface in a large tank of water. - A' shows representative swim paths from the first (Day 1) and last (Day 8) training days. - After training, rats with intact hippocampal function take a more direct path to the platform. - (B) Representative performance of young adult and aged rats across 8 days of training (three trials per day). - While both young and aged rats find the platform more efficiently over time, aged rats are less accurate in their search, indicating attenuated hippocampus-dependent learning and memory function. - Notably, deficits are not uniform among the aged rodent population (represented on vertical scatterplot). - A subset of aged rats perform on par with young rats, demonstrating a relative preservation of memory function. - (C) The functionality of the rat prefrontal cortex can be evaluated using delayed response tasks. - Such tasks assess working memory, a flexible form of memory that maintains information for a brief duration (seconds) to help guide current and future action. - The schematic shows a food-motivated, delayed response task that contains three phases per trial. - In the sample phase, rats are presented with one of two sample levers (left or right). - Once the rat chooses the sample lever, a delay phase is initiated which ranges from 0 to 24 s. - Following the delay interval, both levers are extended and the rat must remember and choose the lever presented in the sample phase to receive a food reward. - The lever position in the sample phase is varied randomly across trials such that the rat must rely on trial-unique information to make the correct choice. - Rats can perform many such trials in a single session (>100), and the mean accuracy of performance at different delay intervals provides an index of working memory function. - (D) Both young and aged rats perform comparably, and with a high degree of accuracy, when the delay between the sample and choice phases is brief. - At longer delay intervals, aged rats are disproportionately and significantly impaired. - There are individual differences in performance among aged rats, with some aged rats maintaining working memory function on par with young rats and some demonstrating marked impairment.
glutamate
- glutamate required for consolidation & retrieval - blocking glutamate receptors prevents consolidation and retrieval
reserve hypothesis
- high idea density in early life autobiographies delays onset of symptoms - 80% of low-scoring Roman Catholic nuns eventually contracted Alzheimer's later in life, even when having APOE ε4 allele. - life-long learning increases cognitive capacity and neurogenesis, providing protective effects against dementia - increasing cognitive capacity through lifelong learning encourages neurogenesis, a surplus that provides protective effects from degenerative effects of Alzheimer's - active lifestyle throughout life promotes neurogenesis - in elderly, this reserve of neurons prevents cognitive declines
working memory
- holds information while it is used - delayed match-to-sample tests measures length of working memory - directed by the prefrontal cortex - prefrontal cortex acts as a working memory central executive - A memory function that provides a temporary "register" for information while it is being used.
long term memory
- hours to months - Requires the cortex & an interaction btw the cortex & hippocampus over time
stroop word color test
- in which subjects must read color names as quickly as possible - this is a difficult task, because some of the words are printed in a conflicting color; the researchers believe that the ACC modulates activity in attentional pathways to focus attention on the word's meaning and suppress attention to its color
retrograde amnesia
- inability to access memories that preceded injury, which increases proportionally w/ hippocampal damage extent - damage to CA1 causes minimal retrograde amnesia - damage to entire hippocampal formation results in retrograde amnesia 15 yrs prior - greater retrograde amnesia w/ damage or degeneration of the cortex
place cells
- increase firing when individual is in a specific location in an environment - collectively form a "spatial map" - dependent on environmental cues and landmarks - also found in humans and primates - place cells are another example of localized storage. - place memory depends on cells in the hippocampus, which increase their firing when the individual is in a specific location in the environment. - the place fields of these cells form a "spatial map" of an environment, which is then adjusted upon entering a new environment and restored on return to the original location. - the fields depend on cues in the environment. - humans have place cells too, that are so precise that the investigators could determine the subject's "location" in a virtual environment.
consciousness
- indicates a sense of conscious experience - state involving awareness of something - holds some things in attention while others recede to background - involves memory - sense of self - vary in level (coma to mania) - Result from the interaction of widely distributed brain structures - Prefrontal parietal network is important to awareness & to consciousness in general
hippocampal formation
- info is temporarily stored in the hippocampal formation - Deals with complex types of memory (e.g. episodic, relational, and spatial memory. DOES NOT HOLD MEMORY. Includes the Dentate Gyrus, Hippocampus, Subiculum, and Fornix.
declarative memory
- involves learning that results in memories of facts, people & events which a person can verbalize - declarative memory is usually affected by amnesia - hippocampus is required for the formation of new declarative memories - knowing facts, people & events - called the "what" in memory - requires hippocampus - amygdala is involved: memories of emotional events
claustrum
- is the "center" of consciousness - proposed as a consciousness executive largely b/c of its interconnections w/ other parts of the brain
state-dependent learning
- material learned in one state is difficult to recall in the other state
delayed matching to sample task
- measures length of working memory
non-declarative memory
- memories of behaviors, skills, procedures, emotions, or stimulus-response conditioning. - called the "how" in memory - HM had his non-declarative memory intact - result of procedural (skill) learning, emotional learning, and stimulus response conditioning - examples: mirror drawing task, tower of hanoi - amygdala is involved: unexpected emotional response while performing behavior - requires striatum
prefrontal cortex
- prefrontal area: directs search strategy for retrieval in hippocampus - integrates long-term memory with other information - manages strategies and decision making - directs working memory traffic in brain - coordinates sensory and motor systems - cells in the prefrontal cortex serve this role, continuing to fire during a delay, even in spite of a distracting stimulus. - the prefrontal cortex also acts as a working memory central executive. - it manages behavioral strategies and decision making. - it directs the neural traffic in working memory. - it coordinates activity involved in perception and response. - active when a subject becomes aware of a relationship between stimuli
alzheimer's disease
- progressive brain deterioration, declarative memory loss - language, visuo-spatial functions, reason, and aggressive problems - affects 10% of people over 65, 50% of individuals over 85. - amyloid plaques & neurofibrillary tangles - global loss of neurons in brain particularly the temporal/frontal lobes. - enlargement of ventricles - hippocampus is isolated from the rest of the brain - 4 genes confirmed in Alzheimer's disease (50% cases): -- 3 Early-onset (<60 years) -- 1 Late-onset (>60 years) - APOE ε4 allele increases risk 3-8x, associated with plaques and tangle formation - Environmental correlates to Alzheimer's: -- lead exposure in childhood -- pesticides (like DDT, still used in some countries) -- chronic stress - neural causes and Treatments -- treatments slow down decline, but cannot reverse effects - detecting Alzheimer's Disease: -- brain scans (PET, MRI) can reveal: atrophy in temporal and parietal areas -- biomarkers for plaques is much more promising (25% of individuals with high levels of plaques contract Alzheimer's within 3 years; low levels correlate to 2% risk of Alzheimer's) -- Reserve Hypothesis - A disorder characterized by progressive brain deterioration and impairment of memory and other mental abilities; the most common cause of dementia.
striatum
- required for procedural/non-declarative memory - reinforces stimulus-response associations -
short term memory
- seconds to hours - working memory - depends on hippocampus
Eve White & Eve Black
- shy and reserved, Eve White would have blackouts while her alter ego, Eve Black, spent the night on the town dancing and drinking with strange men. The puritanical Eve White would have to deal with the hangover, explain a closetful of expensive clothes she didn't remember buying, and sometimes fend off an amorous stranger she found herself with in a bar - Eve, whose real name is Chris Sizemore, went on to develop 22 different personalities before she successfully integrated them into a single self
consolidation
- stages of consolidation: -- short-term (working) memory -- long-term memory -- long-lasting memory - consolidation of new memory into long-term memory is time dependent - time-dependent stages of memory are based on independent processes acting in parallel - later stages of consolidation resulting in memory lasting a lifetime likely involve interaction of brain systems in reorganizing and stabilizing distributed connections. - glutamate is required for consolidation - blocking glutamate receptors prevents consolidation - disabling hippocampus causes consolidation problems in humans
amygdala
- stimulus-reward contingencies in the absence of a response - required for both non-declarative & declarative memories - activates the hippocampus - Strengthens even declarative memories about emotional events apparently by increasing activity in the hippocampus - Electrical stimulation of the amygdala activates the hippocampus & it enhances learning of a nonemotional task (choice maze) - Memory for both pleasant & aversive emotional material is related to the amount of activity in both amygdalas
split-brain patients
- surgical separation of the hemispheres - observe different aspects of consciousness - besides providing a unique opportunity to study the differing roles of the two hemispheres, split-brain patients also raise important questions about consciousness and the self - their hemispheres often engage in independent or even conflicting behavior
tower of hanoi
- task is to relocate the rings in order onto another post by moving them one at a time and without ever placing a larger ring over a smaller one. - procedural learning
sense of agency
- the attribution of an action or effect to ourselves rather than to another person or external force. - sense of agency is mediated by the anterior insula and the inferior parietal area - angular gyrus contributes to the sense of agency by detecting discrepancies between actions and consequences
Henry Molaison
- treated for frequent epileptic seizures - surgically removed hippocampal formation, amygdala - HM is missing amygdala, hippocampus & other structures - symptoms of surgery: --- anterograde amnesia --- retrograde amnesia (extending from time of surgery back to about the age of 16)
anterograde amnesia
- unable to form new memories - damage to CA1 results in moderate anterograde amnesia - damage to entire hippocampus results in severe anterograde amnesia
sense of self
- would likely be severely impaired by the loss of long term, but not necessarily short-term, memory - confabulation suggests the importance of memory to self identity - Includes an identity ("I") & a sense of agency - Frontal-temporal damage impairs episodic memory and may produce a detachment from the self - Anterior cingulate cortex & insula active when people recognize their own face, identify memories as their own, or recognize descriptions of themselves - Body image contributes to a sense of self - Sense of self requires the distinction btw our self & other selves & some understanding of other selves - Body image, memory & mirror neurons contribute to sense of self
dorsal attention network
allocates attention under goal directed control
Which protein is implicated in all genes known to influence the development of Alzheimer's disease
amyloid
consciousness involves...
awareness, attention and a sense of self
What type of memory is impaired in the early stages of Alzheimer's Disease?
declarative memory
(t/f) Blocking glutamate receptors increases memory
false
(t/f) H.M. could not remember his childhood.
false
(t/f) Retrograde amnesia is an inability to form new memories
false
(t/f) Severing the corpus callosum divides the self
false
(t/f) The claustrum is the "center" of consciousness.
false
Damage to this structure will most likely produce anterograde amnesia
hippocampus
awareness
prefrontal parietal network is important to awareness - brain areas important to awareness: prefrontal cortex, hippocampus and parietal lobes - hippocampus: important due to its role in declarative learning - prefrontal cortex: active when a subject becomes aware of a relationship between stimuli - parietal lobes: important in awareness due to its ability to locate objects in space; considered necessary for combining an object's features into a conscious whole
Neurofibrillary tangles in this cortical lobe disconnects the hippocampus from the rest of the brain.
temporal lobe
(t/f) Attention is a key component of consciousness
true
(t/f) Degeneration of cholinergic neurons is associated with Alzheimer's Disease.
true
(t/f) Dissociate identity disorder is associated with childhood physical and/or sexual abuse
true
(t/f) Higher incidence of Alzheimer's disease is associated with lead exposure.
true
(t/f) Place cells respond when an individual is at a particular location in a particular environment.
true
(t/f) Your body image contributes to the sense of self
true
