Cognition and Memory

Question 1

Explain the role of Norepinephrine in depression.

Answer 1

Disruption of noradrenergic pathway through the limbic system are implicated in clinical depression.

It is known that increased ECF (NE) causes elation
Decreased NE causes depression.

This can be traeted with drugs which increase effects of NE e.g. by blocking reuptake of NE (tricyclic antidepressants)
-Also treated with Exercise and SSRI

Question 2

Describe the use of exercise to treat depression

Answer 2

Exercise is now recognised as beneficial in treating mild clinical depression and associated with increased NE
(exercise alse increases endorphin release)

Question 3

Describe the use of SSRI’s to treat depression

Answer 3

Another approach is to block serotonin (5HT) reuptake.
Prozac is an SSRI = Serotonin Specific Reuptake Inhibitor

However, now known that drugs which block NE repute (tricyclic antidepressents) also inhibit serotonin reuptake and both classes of drug take 4-6 weeks before having an antidepressent effect even though increases in transmitter levels occur more or less immediately.

This is because it may take time to make more serotonin receptore but this isnt fully understood

Question 4

Why do some people become very aggressive and violent on Prozac and act out of character?

Answer 4

Complex interactions between NE, 5HT, ACh, DA act in balance with each other as neuromodulators of the limbic system.

They have modulatory effects on attention, motivation, wakefulness, memory, mood, motor control and metabolism

Question 5

How does Adenosine act as a neuromodulator?

Answer 5

Recently shown to be a neuromodulator.

May be involved in suppressing wakefulness as well as causing depression.

Both coffee and chocolate contain compounds that act to inhibit adenosine, (both known since ancient times for their stimulant activity)

Question 6

What is declerative (or conscious) memory?

Answer 6

Episodic Memory
-Memory for events

Sementic Memory
-Memory for words, rules and language

Question 7

What is non-declerative memory?

Answer 7

Relates to e.g. reflex skills learning and is based in areas such as the cerebellum

Question 8

How can memory be divided?

Answer 8

Immediate memory:

• a few 100ms -> 20 secs
• Relates to process of sensory transduction

Short-term memory:
-1 sec -> a few hours

Long term memory
-30 minutes -> decades, centuries

Question 9

What is short term memory?

Answer 9

Its an electrical phenomenon, stored largely in the cortex.

It needs maintained excitation from reverberating circuits i.e. they need to be constantly refreshed

Brief excitatory input -> long lasting neural activity via the circulation of activity among neurones that excite each other

The reverberating circuit keeps alive the evanescent short term memory.
The importance of this can be seen when the refreshing effect is interrupted. (a swift blow to the head resulting in loss of consciousness)

Question 10

Describe the loss of memory after an injury

Answer 10

RETROGRADE AMNESIA:
-cant remember immediate events for up to 4 hours before the injury, although recall of events that happened a long time ago is unaffected.

If the injury is very complicated/severe, there may also be ANTEROGRADE AMNESIA
-an inability to remember events occuring shortly after regaining consciousness, presumably because the cortical function is still disturbed.

Question 11

Describe the use of ECT

Answer 11

Another way to wipe out electrical activity in short term memory is by applying large electrical shocks to the head = ECT

Can be successful in treating schizophrenia or depression.
-> increased NE by downregulating pre-synaptic receptors which inhibit NE release

Question 12

Where is the memory store?

Answer 12

In the sensory and assocciation areas of the cortex

Question 13

How is short term memory converted to long term memory?

Answer 13

Process of CONSOLIDATION.
This involves selective strengthening of synaptic connections by REPEATED USE.
This process is very similar to that which occurs in the cerebellum during motor learning.

Involves facilitation at synaptic sites,
-increased calcium causes gene activation, protein synthesis and structural changes to synapse (TAKES TIME)

During consolidation process, memory (engram) exists as electrical activity and is vulnerable to being wiped

Question 14

How does the significance of an event play into memory?

Answer 14

The frontal cortex and its association with the reward/punishment centres in the limbic system assess the significance of an event in STM.
If not deemed significant, forgotten

If however, considered useful, the frontal cortex “gates” the so called Papez circuit.
Reverbarating activity then continues between the Papez circuit, the frontal cortex, the sensory and association areas until the consolidation process is complete

Question 15

Describe the process of consolidation

Answer 15

1. Sensory input enters sensory and association areas
2. Frontal cortex assesses “significance” with the limbic system reward and punishment areas.
3. If significant its sent to the sensory and association areas which send it to the Papez circuit
   (Papez circuit gated by frontal cortex determination of significance)
4. Memory cycles through Papez circuit being consolidated.
5. Occasionaly levaes limbic system for cortex to decide if its still significant.
6. if still significant keep rewriting into long term memory

Question 16

What makes up the Papez circuit of the limbic system?

Answer 16

Hippocampus
Maxillary body
Anterior thalmus
Cingulate gyrus
Back to Hippocampus

Question 17

Different components of a memory are laid down in different parts of the cortex (e.g. visual component in the visual cortex, auditory in auditory cortex etc).
How does this effect recall?

Answer 17

Memory has to be reassembled.
Recall can be evoked by multiple associations.

Oflaftory stimuli are particulary powerful in evoking long-term memories. (intimately related to the limbic system)

Many memories have strong emotional components to them (i.e. plesant or unpleasant)

Question 18

How does the hippocampus play into consolidation?

Answer 18

The hippocampus is particularly important in consolidation.
Its structure and connectivity are similar to that of the cerebellum.

People with bilateral hippocampal damage have immediate memory and intact long-term memory, but are unable to form new long-term memories.

Their cerebellar memory is intact
The effect is TOTALLY DEVASTATING

Question 19

Discuss Clive Wearing, a muscician who has a herpes simplex virus infection which caused bilateral hippocampal destruction after encephalitis

Answer 19

His is in a permanent state of retrograde and anterograde amnesia.

Lives in a “snapshot of time” with no continuity with his past.
Recognises his wife when she enters the room but when she leaves and returns he says he hasnt seen her for years.
Endlessly writes the same thing but cannot recognise it because even as he sees it, it is fading from his memory.

Question 20

How important are our memories?

Answer 20

We are our memories.

If we cannot make them we lose our connections to our past and who we are

Question 21

What is Korsakoff’s syndrome?

Answer 21

Chronic alcoholism, there is Vitamin B1 deficiency and malnutrition -> mamillary body damage.
The ability to consolidate memory is impaired

Question 22

What is alzheimer’s disease?

Answer 22

There is a sever loss of cholinergic neurons throughout the brain, including the hippocampus.

There is gross memory impairment, with progressive loss of cognitive function.
Some improvement in Alzheimer’s may be seen with anticholinesterases early in disease, but underlying degeneration continues

Question 23

What is the Deja vu phenomenon?

Answer 23

Feeling of familiarity with new events or surroundings can occur normally and is quite common in the aura phase of epilepsy.
Stimulation of parts of the temporal lobes can produce either this or a feeling of strangeness in familiar surroundings.
As if temporal lobe is mis-matching the feelings to the situation, putting an inappropriate “emotional memory” onto an experience.

Question 24

How do we know REM is important?

Answer 24

15-20% of the total existance of placental mammals is spent in REM. This together with the phenomenon of REM rebound indicates very strongly that it must have a very important physiological significance.

Question 25

Is dreaming related to memory consolidation?

Answer 25

Subjects deprived of REM sleep show impairment of memory consolidation for the most complex cognitive tasks
(mental arithmatic), but no overt psychological symptoms (maximum duration of studies only 16 days)

Patients with Korsakoff’s syndrome or Alzheimer’s have greatly reduced REM sleep (Cholinergic neurones from GTF responsible for REM)

Dreaming may enable memory consolifation, reinforce weak circuits.

Question 26

How does dream content vary thoughout the night?

Answer 26

Early on it is very easily explainable in terms of day’s activities, later on in the night can be very bizarre, often very old memories, most strange and most remembered because most likely to awaken.

Question 27

How may dreaming be involved with repackaging memories?

Answer 27

Dreaming may be to tidy up the memory stores so that the same information can be packaged more compactly.
A bit like tidying an office.
Deal with the new stuff on the desk first then with more time go through alder material in the bottom of the filing cabinet.

Dreaming may help to forget memories that are no longer useful.

Question 28

What are the dreams of blind people like?

Answer 28

People who are born blind have auditory dreams.

People who go blind gradually lose the ability to have visual dreams