Frontal Lobes, Hippocampus, and Cerebral Cortex

Question 1

Effects of DLPFC lesion

Answer 1

Inability to use intention (goals) to modulate attention (task at hand) leading to perseveration (failure to switch attention appropriately); requires excessive environmental cues in order to accomplish a task (environmental dependency)

Question 2

Environmental dependency

Answer 2

Characterized by requiring excessive environmental cues in order to accomplish a task; results from lesion of the DLPFC, which is responsible for application of intention (goals) to attention (task at hand)

Question 3

Effects of VMPFC lesion

Answer 3

Behavioral disorder characterized by an inability to anticipate the risk/reward profile of behavior leading to behavioral disinhibition of risky behaviors

Question 4

ACC - Normal function & effects of lesion

Answer 4

ACC is active during focused mental effort - it detects conflict between current attention/behavior and desired results, and promotes action toward goal (motivation)

Lesion causes abulia (loss of will)

Question 5

Hippocampal circuitry

Answer 5

Entorhinal cortex to dentate gyrus via perforant path; granule cells of dentate gyrus to pyramidal cells of hippocampus CA3 pyramidal cells via mossy fibers; granule cells in CA3 project to CA1 (Schaffer collaterals), to mammillary bodies (via fornix), and back to CA3 (auto-associations); CA1 projects to entorhinal cortex via subiculum; entorhinal cortex projects to cortical association areas

Question 6

Neotcortex (Isocortex)

Answer 6

6 layered cortex - makes up most of the cortex

Question 7

Granular cortex

Answer 7

Primary specialized function is to receive input; i.e. most cortical sensory input areas (visual cortex, somatosensory cortex, etc.)

Question 8

Agranular cortex

Answer 8

Characterized by poor development of granule cell layers and prominence of pyramidal cell layers

Primary motor and premotor cortex (Broadman’s areas 4 and 6) are the only areas designated as agranular; prominent pyramidal layer suggests a function mostly concerned with output

Question 9

Layer IV

Answer 9

Granule cell layer; receives ascending input and internally relays to layer III

Question 10

EEG

Answer 10

Measures electrical potential fluctuations at the scalp produced by temporal and spatial summation of EPSPs and IPSPs induced in pyramidal neurons of the cortex

Records current flow along a large population of cells with multiple inputs, 20% of which are inhibitory; synchronized, alternating patterns of depolarization and hyperpolarization of a large number of neurons in a given locationg ive rise to patterns of oscillations

Question 11

Delta frequency

Answer 11

< 3.5 Hz

Deep, dreamless sleep

Question 12

Theta frequency

Answer 12

4-7.5 Hz

Drowsiness

Question 13

Alpha frequency

Answer 13

8-13 Hz

Restfulness wakefulness (inattention)
Disappear during conscious attention to stimuli

Question 14

Beta frequency

Answer 14

14 - 30 Hz

Alert, concentrating, attentive
REM sleep

Question 15

Alpha frequency

Answer 15

30 - 100 Hz

Question 16

Conductor-led model

Answer 16

Rhythmic burst firing in the thalamus is prevalent when the reticular nucleus is active, i.e. slow wave sleep

Cholinergic input from brainstem depolarizes thalamic relay neurons; activation of relay neurons inhibits thalamic reticular neurons, promoting the steady train of thalamic relay activity which opens the thalamocortical gate to sensory information

Question 17

What is the ‘conductor’ in the conductor-led model of neuronal synchronicity?

Answer 17

ACh from the brainstem; ACh depolarizes thalamic relay neurons

Question 18

Self-organizing ensemble model of neuronal synchronicity

Answer 18

Interconnected inteurons randomly discharge together, imposing stronger inhibition on shared targets and increasing the probability that those neurons will then fire together upon recovery; creates time windows in which cells can fire / wire together

Frequency of oscillation depends on the average duration of inhibition; if inhibition is mediated by fast-acting GABA-A receptors, oscillation corresponds to the gamma frequency (40 -100Hz)