Anatomy and function of the temporal lobes: L11

Question 1

define epilepsia

Answer 1

epileptic seizures arise from sudden excitation in groups of neurons with a loss of inhibitory potential

Question 2

1. excitatory synapse
   - neuro transmitter
   - action
2. inhibitory synapse
   - neuro transmitter
   - action

Answer 2

1. glutamate
   - increases the spread of excitation
2. GABA (gamma-amino-butyric acid)
   - increases nervous system stability

Question 3

definition of TLE (temporal love epilepsy)

- 2 types of seizures

Answer 3

• recurrent unprovoked seizures originating from medial or lateral temporal lobe
  1. simple partial seizures (no loss of awareness)
  2. complex partial seizures (loss of awareness)

Question 4

pathophysiology (cause) of TLE (3)

-> what can cure/reduce number of Szs?

Answer 4

1. hippocampal sclerosis (HS)
   = excess growth of glial cells after neuronal cell loss
2. occurs early in life
3. past infections, tumours & vascular malformations
   -> surgical removal of the lesioned hippocampus

Question 5

1. grey brain matter contains

2. white matter contains

Answer 5

1. many neurons

2. axons and joining sections of neurons

Question 6

what is a sagittal section of the brain?

Answer 6

side view / cross section

Question 7

what did HM (henry molasion)

1. suffer with?
2. undergo?

Answer 7

1. severe TLE
2. bilateral resection of extensive amount of medial temporal tissue -> incl. amygdala, hippocampi and part of parahippocampal gyrus

Question 8

HM temporal lobe removal resulted in…

Answer 8

1. reduction in seizures
2. retained IQ & attention span
3. retrograde memory (prior to surgery) recovered over time (after 2 years), except he never remembered 6 months prior to surgery
4. anterograde amnesia - impairment for memories created after injury (learning novel information)

Question 9

define
1. declarative
2. procedural
memory

Answer 9

1. conscious access to information learnt previously

2. remembering ‘how to’ (e.g. riding a bike)

Question 10

HM’s memory post-op- death

1. declarative
2. procedural

Answer 10

1. severely impaired:
   - unable to recall faces & names
   - language frozen in the 1950s
2. continued intact:
   - able to learn new skills, no recall of learning them
   - normal performance on procedural memory tasks

Question 11

HM procedural memory task results

Answer 11

• day 1-3
• gradual improvement (typical of someone with good procedural memory)
• trace star
• became better and better (sheer drop in errors day 1 -> lower errors day 2 -> very few errors day 3)
• he didn’t remember ever doing the task

Question 12

what does HM tell us about memory?

- medial temporal lobe structures are…

Answer 12

• essential for memory function
• more essential for anterograde than retrograde memory
• distinction between declarative & procedural memory

Question 13

what have we learnt since HM? (3)

Answer 13

1. intact memory function relies on a neuroanatomical network involving many brain regions
2. TL are the ‘engine’ of memory
3. functional asymmetry between 2 lobes

Question 14

1. left MTL lesions =

2. right MTL lesions =

Answer 14

1. verbal memory impairment

2. visual memory impairment

Question 15

What is the hippocampus in relation to memory?

• also known as (short form)
• hippocampal formation

Answer 15

• supports memory
• cornu ammonis (CA1 - CA3)
• formation: dentate gyrus + CA1 - CA3 + subiculum

Question 16

how memory works 4 steps (brain regions)

- pathway name

Answer 16

dentate gyrus -> mossy fibres -> CA3 -> CA1 -> subiculum

- preforant pathway

Question 17

schematic representation of MTL

-> how are memories accessed?

Answer 17

• information is integrated into sensory systems & sent to hippocampal formation for long-term storage
• > reciprocal connections between hippocampal formation and temporal neocortex

Question 18

Role of hippocampal formation

Answer 18

• learning and consolidating novel information

Question 19

what is consolidation theory? (Squire)

Answer 19

• after a period of consolidation, information can be retrieved independently of hippocampal formation involvement

Question 20

what is multiple trace theory? (Moscovitch)

Answer 20

• retrieval of autobiographical/episodic experiences always involves hippocampal formation

Question 21

what is the hippocampal formation particular necessary for?

Answer 21

relational memory tasks
-> paired associate learning tasks (remember associations between unrelated pieces of information i.e. word & object)