W6L1 - HM and Temporal Lobes
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What does HM have initially
Severe epilepsy
What are epilepsy seizures caused by
Sudden excitation in groups of neurons, with a loss of inhibitory potential
What is the biochemistry behind seizures
Inhibitory: GABA - Increases nervous system stability Excitation: Glutamate - Increases spread of excitation Seizures decreases GABA.
Definition of Temporal Lobe Epilepsy (TLE)
Recurrent unprovoked seizures originating from medial or lateral temporal lobe
What are the types of TLE
• ) Simple partial seizures (without loss of awareness) 2. ) Complex partial seizures (with loss of awareness)
What is the most common pathphysiology (disordered physiological processes associated with injury) of TLE
Hippocampal sclerosis (HS)
What is hippocampal sclerosis (HS) caused by
• Neuronal loss - Gliosis (excess growth of glial cells after neuronal cell loss occurs in a region)
Which age does HS occur often
Early in life (About 20)
What happens to seizures when a leisoned hippocampus is surgically removed
Can reduce the number of seizures
How many gyri and sulci of the Temporal Lobe
Gyrus: Superior, Middle, Inferior Sulcus: Superior, Inferior
Where is the hippocampus located
Within the parahippoocampal gyrus (MTL)
What is the parahippocampal gyrus posterior to
Anterior: Perihinal Middle: Entorhinal Posterior: Parahippocampal Gyrus
What did HM undergo. Which parts of his brain was removed
Bilateral resection of extensive amount of medial temporal tissue (Amygdala, Hippocampi, part of parahippocampal gyrus)
What did HM retain after surgery
Normal attention span Normal Intelligence Retrograde memory recovered over time
What is the difference between retrograde amnesia and anterograde amnesia
Retrograde: Impairment for memory PRIOR to injury Anterograde: Impairment for memory AFTER injury
What condition did HM have after surgery
Severe antereograde amnesia (particular declarative memory)
What is the difference between declarative and procedural memory
Declarative: Conscious access to information learnt previously Procedural: “Muscle Memory”/”How To” (playing piano)
DId HM lose declarative/procedural memory. How do we know?
Declarative: Severely impaired Procedural: Retained Able to learn new skills and normal performance on procedural memory task (star)
What did HM tell us about memory and MTL
1) Essential for memory function 2) More essential for anterograde than retrograde memory 3) Distinction between Declarative and Procedural memory
Anatomy of Memory: What have we learnt since HM
Intact memory function relies on a neuroanatomical network (many regions) Temporal Lobes (TL) are the ‘engine’ of memory.
Memory function in TLE patients
‘Material-specific’ memory deficits related to involved medial temporal lobe (MTL) Left leision: Verbal Impairment Right leision: Non-Verbal/Visual Impairment
What is the hippocampus also known as
Cornu Ammonis: CA1 to CA3
Hippocampal formation
Dentate Gyrus + CA3 - CA1 + Subiculum
What is the schematic representation and processes of the MTL
Unimodal/Polymodal Association <> Perihinal Cortex + Parahippocampal Cortex <> Entorhinal Cortex <> Hippocampal Formation Information flows from sensory and sent to hippocampal for long-term storage. Memory assessed by hippocampal formation to temporal neocortex