8.0 Neuropsychology of memory & learning

Memory is the ability to

• store information & events from the past, retrieve them and bring to consciousness the information that has been learned

Memory is an essential cognitive function composed of

• several systems (sensory memory, short-term memory & long-term memory) & processes (encoding, storage and retrieval of information) that depend on different anatomical structures.

 Learning processes and memory depend on

• other cognitive processes

• attention, perception etc.,

Memory helps us to 

• know everything that is necessary to be able to adapt to our environment in the most optimal way (avoid risk situations, maintain social and ethical norms, etc.).

Amnesia

• Partial or total loss of memory

Multiple Memory Systems

• Different kinds of learning & memory use independent neural processes

process of memory

Short-term memory

• known as temporal memory/working memory

• Memory for recent events & their order.

• Information quantity & limited duration (7±2 items; seconds)

• Mediated by locations defined by the dorsal & ventral pathways to 2 regions of the frontal cortex

Left-posterior-temporal lesion may lead to (STM + Temporal lobes)

• Short-term memory deficits

Frontal-lobe patients showed (STM + frontal lobe)

• strong proactive interference

Areas involved in STM + frontal lobe

• Dorsolateral prefrontal cortex

• Ventrolateral prefrontal cortex

Dorsolateral prefrontal cortex

• manipulation of information & creation of strategies and action plans → Working memory

Ventrolateral prefrontal cortex

• maintenance, transfer processes & maintenance of information → STM 

Left hemisphere:

• Phonological loop

Right hemisphere

• Visuospatial sketchpad

Long-term explicit memory

• “warehouse” with “unlimited” capacity & duration → not always able to access stored information

Explicit memory

• Events, facts, & episodic memories

• Conscious intentional remembering

• Recall of information is greatly influenced by the way in which the information was originally processed.

Personal experiences

• episodic memories

• autobiographical

facts

• semantic memories

• knowledge

Episodic memory

• Autobiographic

• Person’s recall of singular personal events

• Life experiences centered on the person himself or herself: life history.

Episodic memory provides a sense of

• continuity → autonoetic awareness

Autonoetic awareness

• Awareness of our self as a continuous entity through time “Time travel” → past, present and future

K.C patient

• experienced a cerebral diffuse lesion

• After TBI, had dense amnesia for personal experiences

• Could not imagine future any more than he could remember past

What brain areas are important for episodic memory?

• The medial temporal lobe and ventral prefrontal cortex, connected by the uncinate fasciculus.

Semantic memory

• All nonautobiographical knowledge —knowledge about the world.

• Ability to recognize family, friends, & acquaintances; information learned in school; & knowledge of historical events & of historical and literary figures.

• Knowledge codified in a conceptual way

In H.M & K.C case the semantic memory was

• intact (preserved)

Brain areas involved in the semantic memory

•  the temporal- & frontal-lobe regions adjacent (located close to)to the neural regions that subserve episodic memory.

Neural substrates of explicit memory

• Temporal lobe (hippocampus, rhinal cortices adjacent to it) & prefrontal cortex

• Thalamus

Neural substrates of explicit memory: hippocampus

• Dentate gyrus

• Amnon´s horn

• Perforant pathway

• Fimbria-fornix

Dentate Gyrus

• cells are stellate/granular

• sensory cells

Amnon´s horn

• contains pyramidal cells divided into 4 groups: CA1, CA2, CA3, & CA4

• Motor cells

Perforant pathway

• connection between the hippocampus & the posterior temporal cortex neocortex

Fimbria-fornix

Connects the hippocampus to the thalamus, prefrontal cortex, basal ganglia, & the hypothalamus

Studies of hippocampal patients demonstrate four conclusions:

• Anterograde deficits are more severe than retrograde

• Episodic memories are more affected than semantic memories

• Autobiographic memory is especially severely affected

• Time “travel” is diminished

Neural substrates of explicit memory: temporal cortex

• Temporal-lobe areas border rhinal fissure (called rhinal cortex)

• includes enthorinal & peririhinal cortex

• involves the integration of perceptual pathways in memory: ventral pathway (what) & dorsal pathway (where)

entorhinal & perirhinal cortex regions projects to the

• hippocampus

Ventral pathway

• what

• sends information to the lateral entorhinal & perirhinal cortices → most involved in semantic memory

Dorsal pathway

• where

• sends information to the parahippocampal & medial entorhinal cortices →most involved in episodic memory

Neural substrates of explicit memory: hemispheric specialization

• Right Temporal Cortex

• Left Temporal Cortex

• Parietal & Occipital Cortex

• Frontal cortex

Right Temporal Cortex → lesion leads to

• deficits on face recognition, spatial position, & maze learning

Left Temporal Cortex → lesions leads to

• Deficits in recall of word lists, nonspatial associations, & on the Hebb Recurring-Digits test

Parietal & Occipital Cortex → injuries

• Injuries may produce color amnesia, prosopagnosia, object anomia, & topographic amnesia.

• Many of these deficits appear to develop in the presence of bilateral lesions only

Frontal Cortex → left prefrontal cortex

• More engaged in encoding semantic & episodic information than in retrieving it

Frontal cortex → right prefrontal cortex

• More engaged in episodic information retrieval than left