1. Neuroscience: Exploring the Brain, 3e
Neuroscience: Exploring the Brain, 3e
Chapter 24: Memory Systems

2. Introduction Learning: Lifelong adaptation to environment
Several similarities between experience dependent brain development and learning
Similar mechanisms at different times and in different cortical areas
Memories range from stated facts to ingrained motor patterns
Anatomy: Several memory systems
Evident from brain lesions

3. Types of Memory and Amnesia
Learning: Acquisition of new information
Memory: Retention of learned information
Declarative memory (explicit)
Facts and events
Nondeclarative memory (implicit)
Procedural memory- skills, habits

5. Types of Memory and Amnesia
Long-Term, Short-Term, and Working Memory
Working memory: Temporary information storage
requiring rehearsal
Sensory information
Short-term memory
Consolidation
Long-term
memory
Short-term memory
Sensory information
Consolidation
Long-term
memory
Time

6. Types of Memory and Amnesia
Retrograde amnesia: Forget things you already knew
Anterograde amnesia: Inability to form new memories

7. The Search for the Engram
Lashley’s Studies of Maze Learning in Rats
Engram:
memory trace

8. The Search for the Engram
Hebb and the Cell Assembly
External events are represented by cortical cells
Cells reciprocally interconnected reverberation
Active neurons—cell assembly
Consolidation by “growth process”
“Fire together, wire together”
Hebb and the engram
Widely distributed among linked cells in the assembly
Could involve neurons involved in sensation and perception

9. The Search for the Engram
Hebb’s Cell Assembly and Memory Storage Hypothesis
Distributed Memory

10. The Search for the Engram
Localization of Declarative Memories in the Neocortex
Inferotemporal Cortex (area IT), higher-order visual area in macaques
Lesion impairs discrimination task despite intact visual system at lower levels
Disruption of memory or visual pattern recognition?

11. The Search for the Engram
Localization of Declarative Memories in the Neocortex
At first, all cells respond to newly presented faces the same amount
With repeated exposures, some faces evoke a greater response than others - i.e., cells become more selective
(Adapted from Rolls et al., 1989 Exp Brain Res 76: , Figure 1.)

12. The Search for the Engram
Electrical Stimulation of the Human Temporal Lobes
Temporal lobe stimulation
Different from stimulation of other areas of neocortex
Penfield’s experiments
Stimulation -> Sensations like hallucinations, recall past experiences
Temporal lobe: Role in memory storage
Caveat: Minority of patients, all had epilepsy

13. The Temporal Lobes and Declarative Memory
The Effects of Temporal Lobectomy (HM)

14. The Temporal Lobes and Declarative Memory
The Medial Temporal Lobes and Declarative Memory

15. The Temporal Lobes and Declarative Memory
The Effects of Temporal Lobectomy (HM)
Removal of temporal lobes had no effect on perception, intelligence, personality
Anterograde amnesia so profound could not perform basic human activities (and partial retrograde amnesia)
Never recognized Brenda Milner, who had studied him for nearly 50 years
Impaired declarative memory, but spared procedural memory (mirror drawing)

16. http://youtu.be/SoxsMMV538U http://youtu.be/SoxsMMV538U
Memory capacity: Jill Price

17. The Temporal Lobes and Declarative Memory
The Medial Temporal Lobes and Declarative Memory
Information flow through medial temporal lobe

18. The Temporal Lobes and Declarative Memory
The Medial Temporal Lobes and Memory Processing (Cont’d)
DNMS: Delayed non-match to sample
Medial temporal lobe structures: Important for memory consolidation

19. The Temporal Lobes and Declarative Memory
The Medial Temporal Lobes and Memory Processing (Cont’d)
Effect of medial temporal lobe lesions on DNMS
Recognition memory

20. The Temporal Lobes and Declarative Memory
The Diencephalon and Memory Processing
Brain regions associated with memory and amnesia outside the temporal lobe

21. The Temporal Lobes and Declarative Memory
The Diencephalon and Memory Processing
Radio technician 1959 accidentally stabbed through left dorsomedial thalamus with fencing foil
Less severe but like HM; anterograde and some retrograde amnesia
Korsakoff’s Syndrome: Alcoholics - thiamin deficiency
Symptoms: Confusion, confabulations, severe memory impairment, apathy, abnormal eye movements, loss of coordination, tremors
Lesions to dorsomedial thalamus and mamillary bodies
Treatment: Supplemental thiamin

22. The Temporal Lobes and Declarative Memory
Memory Functions of the Hippocampus
Hippocampal responses to old (familiar) and new stimuli

23. The Temporal Lobes and Declarative Memory
Radial arm maze (a)
(b) Normal rats go down each arm for food only once, but with hippocampal lesions revisit arms already explored
(c) Normal and lesioned rats learn which arms are baited and avoid the rest, but still revisit arms (don’t remember that they have already taken the food from the arm).

24. The Temporal Lobes and Declarative Memory
The Temporal Lobes and Declarative Memory
Spatial Memory and Hippocampal Place Cells
Morris water maze: requires NMDA receptors in hippocampus.
Place cells fire when animal is in a specific place.
Dynamic: Place fields develop as rat becomes familiar with environment
Do ‘Place cells’ really code for place?
Linear maze; restraint experiments

25. Place cells Grid Cells

26. Place field:

27. Place cell activity http://www. youtube. com/watch

28. The Temporal Lobes and Declarative Memory
The Temporal Lobes and Declarative Memory
Spatial Memory and Hippocampal Place Cells
Morris water maze: requires NMDA receptors in hippocampus.
Place cells fire when animal is in a specific place.
Dynamic: Place fields develop as rat becomes familiar with environment
Do ‘Place cells’ really code for place?
Linear maze; restraint experiments.
Relational hypothesis

29. Causal role of hippocampal cell activity in establishing associative memories
c-fos-tTA transgenic mice: promoter of the c-fos gene drives the expression of the tetracycline transactivator (tTA) to induce expression of a gene downstream of the tetracycline-responsive element (TRE) (8–12). Inject AAV4 virus encoding TRE-ChR2-mCherry into the DG or CA1 of c-fos-tTA animals

30. The Temporal Lobes and Declarative Memory
Spatial Memory and Hippocampal Place Cells
PET imaging in human brain related to spatial navigation of a virtual town
Single neuron recording (Epilepsy patients)- ‘place cells’ exist in human hippocampus

31. The Striatum and Procedural Memory
Caudate nucleus + Putamen = Striatum
Lesions to striatum disrupt procedural memory (habit learning)
Standard radial arm maze depends on hippocampus
Modified radial arm maze, with lighted arms, depends on striatum; learn assoc. (food at lighted arms).
Damaged hippocampal system: Degraded performance on standard maze task
Damaged striatum: Impaired performance of the modified task; ‘Double dissociation’ of lesion site and behavioral deficit.

32. The Striatum and Procedural Memory
Habit Learning in Humans and Nonhuman Primates
Parkinson’s patients show that human striatum plays a role in procedural memory
Declarative

33. The Neocortex and Working Memory
The Prefrontal Cortex and Working Memory
Primates have a large frontal lobe
Function of prefrontal cortex: self-awareness, capacity for planning and problem solving

34. The Neocortex and Working Memory

35. The Neocortex and Working Memory
The Prefrontal Cortex and Working Memory
Working memory activity in monkey prefrontal cortex

36. The Neocortex and Working Memory
The Prefrontal Cortex and Working Memory
Wisconsin card-sorting task

37. The Neocortex and Working Memory
The Prefrontal Cortex and Working Memory (Cont’d)
Imaging Working Memory in the Human Brain
Six frontal lobe areas show sustained activity correlated with working memory
Blue: Facial memory
Green: Facial and spatial memory

38. The Neocortex and Working Memory
Lateral Intraparietal Cortex (Area LIP) and Working Memory
Area LIP: Guiding eye movements -Delayed-saccade task
Like ‘QV’ cells in S.C.- activity ‘holds’ motor error info

39. Concluding Remarks Learning and memory Occur throughout the brain
Memories
Duration, kind of information stored, and brain structures involved
Distinct types of memory
Different types of amnesia
Multiple brain systems for memory storage
Engrams in temporal lobe neocortex
Physiological basis?
Long-term memories: structural basis?

40. End of Presentation

41. Types of Memory and Amnesia
Amnesia: Serious loss of memory and/or ability to learn
Causes: Concussion, chronic alcoholism, encephalitis, brain tumor, stroke
Limited amnesia (common)
Dissociated amnesia: No other cognitive deficit (rare)

42. Types of Memory and Amnesia
Amnesia (Cont’d)
Transient global amnesia: Shorter period, temporary ischemia (e.g., severe blow to head)
Symptoms: Disoriented, ask same questions repeatedly; Attacks subside in couple of hours; Permanent memory gap

43. The Search for the Engram
Localization of Declarative Memories in the Neocortex
Human extrastriate cortex differentially activated in car and bird experts