exam Flashcards
Explain the difference between egocentric and allocentric spatial frames of reference.
Egocentric and allocentric frames of reference:
Egocentric: objects are framed in reference to the self, (where there are in comparison to where the individual is)
Allocentric: framed in reference to each other (but includes self), where they are in comparison to where other objects are
>Absolute: unchanging
>Intrinsic: depends on orientation of reference object
Provide an overview of some wayfinding techniques used for spatial navigation and representation.
Categorical techniques: qualitative or nominal
Above, near, on, under
Lateralized for left cerebral hemisphere, not language based
Left parietal cortex
Coordinate: qualitative or metric, numerical
N times as far, X degrees west, 7 km, etc.
Lateralized to right cerebral hemisphere
Right parietal cortex
Outline some distinct ways in which aspects of spatial representation are processed in the brain.
Different cells process different aspects of spatial representation:
-Place cells: receive input from grid cells, code for specific places
-Located in dentage gyrus
-Grid cells: received multimodal input and responds to distinct spatial frequencies, created a grid-like representation of space in the head
Located in the entorhinal cortex
-Time cells: sensitive to intervals between key events
-Both in dentate gyrus and entorhinal cortex
Additionally, the dorsal stream supports spatial awareness with three output pathways:
-The prefrontal pathway supports spatial working memory
-The premotor pathway supports visually guided action
-The medial temporal cortex supports spatial navigation and wayfinding
What are engram cells? Outline some evidence about the process of how some neurons become engram cells.
Engrams cells are cells that support the existence of an engram, and meet a specific criteria:
Cells must be active during learning
Cells must be active during tests
They can generate an engram when active
They prevent engrams when inhibited
Engram cells are active during both learning and retrieval. They can be blocked or distinctly activated.
Engram cells are a type of neuron.
Provide a full classification outline of different memory systems in humans.
Two ways to organize memory types: Duration and Types of information stored in LTM
Duration
- Sensory buffer (extremely short)
- Short-term memory
- Intermediate term memory
- Long term memory (LTM)
Types of stored information in LTM
- Declarative
> Episodic and semantic
- Nondeclarative (procedural)
> Skills, priming, conditioning
Compare and contrast the unitary and modular views of the structure and functions medial hippocampal system.
The unitary view: all hippocampal structures are involved with declarative memory production, and require the MTH system
Modular view: only the episodic memories require the entire MTH system
The unitary view posits that damage to any part of this system will produce the same level of impairment in episodic + semantic memory
Due to patients like RH and VC, the hippocampus is confirmed to have a role in episodic memory, however, the same cannot be said for semantic memory, which weakens the argument for unitary views.
Identify the three properties of episodic memory and briefly describe how the brain supports these properties.
Three properties of episodic memory:
Supports conscious recall of contextual spatiotemporal information for later retrieval
Automatically captures episodic and incidental information about single events in our lives
Includes information about additional spatial and temporal context that is protected from interference by other memory traces
The brain supports this through a hierarchy and a loop:
The hierarchy:
Episodic experiences are transduced by sense receptors then processed hierarchically until they reach the hippocampus
1. Uni and modal associative areas for perception
Perirhinal and parahippocampal cortexes for associated recall
Entorhinal cortex for spatiotemportal event context
The loop:
Supports sequential indexing of integrated event information
EHC -> HC (DG > CA3 > [(ECH->)] CA1) -> SBC -> ECH
Part of unitary view of the medial hippocampal system
What is the hippocampal index theory? Provide a concise but complete description of the theory.
An explanation of how the neural network involving the tiny hippocampus can account for episodic memory processes
Experiences are represented in many cortical regions, and stored in the hippocampus by LTP as an index
When a stimulus/ retrieval cue activated the index, it triggers cortical and subcortical association of an engram
Enough stimuli activates enough of the index to cause the recall of the engram
Having an insufficient subset of information fails to activate the index, causing memory failure
The index does not directly have an stored episodic content, but can react to cues, and acts as an index, retrieving the memory attached to the cue.
Outline some of the data regarding engrams formed perinatally (before and just after birth).
Before:
Olfactory: newborns show interest in what mothers ate during a pregnancy
Can remember melodies presented during 3rd trimester up to a month after birth
Auditory: newborns/ infants respond to familiar voices such as the mother’s voice, and show preferences to the mother’s voice over the father’s, and over strangers as well.
After:
Newborns prefer the mother’s voice over other’s, and sucking patterns show familiarity to distinct voices
Can differentiate between their own and foreign languages
What is childhood (infantile) amnesia? Provide an analytic overview of why it is thought to occur.
Childhood amnesia is a description of the phenomenon in which we don’t have access to the majority of our (episodic) childhood memories, primarily before the age of 4 (according to Freud)/ infancy
There are two processes that are though to account for this:
Vulnerability of early memories
Younger children don’t form or consolidate memories the way adults do
Memory formation strength increases with age
Inaccessibility of childhood memories
Memories are formed and consolidated, but retrieval is blocked
What is the standard model of systems consolidation? Contrast it with cellular consolidation.
The standard model of systems consolidation:
An initial memory traces is set weakly connected to cortical representations
Retrieval initially is dependent on hippocampal connections
As memories age, cortical strength increase (and are therefore consolidated)
There are two types of consolidation, each relating to a different type of memory
Systems consolidation is related to declarative memories only, as procedural memories are not affected by hippocampus damage
Occurs over days to years
Cellular consolidation refers to the strengthening of synapses (like LTP)
Occurs within hours
Procedural and declarative memories have been shown to be separate through cases like H.M.’s
Outline some of the evidence that suggests most age-related cognitive decline (including in memory) is related to degenerative disease rather than typical aging.
Degenerative diseases are connected to a lot of age-related cognitive decline, as the effects of these diseases are what cause these “hallmarks” of aging:
Vascular dementia: Leads to defects in memory formation and retrieval, among others.
Multiple white matter lesions
Severe cognitive deficits
Caused by vascular conditions like hemorrhages, cardiac arrest, etc.
Lewy Body and Frontotemporal dementias:
Lewy body: causes decline in mental ability
Characterized by deposits of α-synuclein proteins in Lewy bodies
Frontotemporal: cluster of dementias related to deterioration of frontal and temporal lobes, which are associated with personality, behaviour, and language
Primary progressive aphasia (can cause aphasia)
Alzheimer’s disease: Severe episodic memory loss and neurodegeneration
Most common cause of dementia
Explain the role of slow-wave sleep in memory consolidation.
SWS is considered the most implicated/ related to memory consolidation out of all sleep stages (especially NREM sleep stages)
During slow wave sleep, slow oscillations arise in the cortex and spread to subcortical areas. In addition, sleep spindles arise from the thalamus and travel to the cortex. Ripples arise in the hippocampus, which are associated with the offline replay of learned sequences during encoding. Synchronization of these rhythms is believed to ensure memory replay and transfer of learned sequences from the hippocampus to the cortex.
The coordination of sleep spindles with hippocampal ripples and neocortical slow oscillations during SWS is in the service of consolidating new memories during sleep. It is thought to cause the transferring of new memories from short-term (depending on the hippocampus) to long-term representation in the neocortex.
Identify five subcortical brain regions involved in regulating sleep, and for each one briefly describe what its contribution to sleep regulation is.
- Serotonergic (raphe nuclei): promotes arousal, wakefulness
- Noradrenergic (locus coeruleus): promotes arousal, wakefulness
- Subcoerulus: inhibits motor neurons, promotes muscle atonia during sleep
- GABA-ergic (basal forebrain): promotes sleepiness, SWS
- Cholinergic (pedunculopontine): promotes REM (PGO waves)
Outline the stages of sleep and for each one describe one of its characteristic roles in memory and/or cognition.
Stage 1: N1
Hippocampus displays theta rhythm
Transitional phase between waking and deep sleep
NREM
Lasts a few minutes
Transitional phase may help prepare the brain for memory processing in later stages
Stage 2: N2
Deeper than N1 but still close to wakefulness
Has sleep spindles (sharp spikes) and K complexes (large slow waves)
Makes up a lot of total sleep during the night
Sleep spindles have been shown to support plasticity
Theta ripples are causally related to memory consolidation
Stage 3: N3
Slow wave sleep/ SWS
Deepest part of sleep
Slow delta waves
Crucial for memory consolidation and schematic development
Stage 4: REM
Beta waves
When you dream/ when dreams are reported
Brain is highly active, but body is normally paralyzed
Important for memory consolidation
Theorized to be related to memory integration and procedural memory consolidation
Explain how sleep is thought to help in the formation of schemas and integration of new memories.
During slow wave sleep, the common parts of different memories are overlapped, which leads to the development of a schema. For example, there are many examples of what a “bird” could be, but the similarities that overlap are what get encoded as a schema. Moreover, during sleep, memories are attached to schemas, and schemas can also get taken apart and restructured for the addition of new information or the formation and integration of new memories.
In bullet points:
- Consolidation of distinct memories removes differences/ retains commonalities, creating a schema.
- During slow wave sleep, commonalities can be activated and reinforced, and the schemas may be updated
- Synaptic down scaling may occur to further remove differences
- Assimilation of new memories is easier when there are schemas.
»_space; A memory sharing information with a schema means that the memory can be appended to the schema and further retained
- Memories can cause updates to schemas
