Working Memory

Question 1

What is diplopic?

Answer 1

Double vision

Question 2

What’s true about human and monkey prefrontal cortex?

Answer 2

They’re homologous

Question 3

Where is the peri principal sulcus?

Answer 3

above and below (around) the principle sulcus

Question 4

Describe Orbitofrontal cortex

Answer 4

Center of limbic, emotion, social

Just in front of the thumb at the bottom of the forebrain

Question 5

Describe the dorsolateral prefrontal cortex

Answer 5

It’s granular, receives input from the thalamus, and center of executive control

In the middle of the prefrontal cortx

Question 6

What is considered weight based and separate from working memory?

Answer 6

episodic memory and the sense that something is familiar or recent

Question 7

What is a classic direct-method delayed response trial and what does it show?

Answer 7

Monkey sees reward go into left or right box, screen is pulled down for some duration (delay), screen is lifted and monkey goes for food.

Monkeys are poor at this task after prefrontal (area 46) lesions. However, after rehabilitation of co-morbid results of the lesions (like neglect), the monkeys do better, but not as well as before the lesion.

When humans do this task, they add a delayed alternation version to show if its just working memory or other forms of memory. Those with other memory disorders due worse on the delayed alternation, but the prefrontal patients do some what bad on both of them though better than the others (except alcoholics) on the delayed alternation. I think the humans had 5 choices

Delayed alternation involves remembering your previous response and choosing a different one based on that response.

Question 8

What is the spatial match-to-sample task and what is shown neuronally?

Answer 8

The monkey uses the center out method and has to wait for a match to an LED it saw flash. When he sees this, he makes an arm movements either towards the flash or to some other place (compatible vs incompatible). This disassociates planning from working memory because the planned incompatible movement is not related to the location of the sample being held in working memory.

Neurons in the monkeys fired for the match even when the lights were firing in other locations, showing that they’re holding that location. They do this regardless of the planned movement direction.

This is not the case for parietal neurons. They cease firing once a stimuli appears in another location. Also, the prefrontal neurons do not fire for the new stimulus.

Question 9

What are Baddeley and Hitch’s parts of working memory?

Answer 9

phonological loop, visuo-spatial scratchpad, episodic bufffer, and manipulating it all (central executive)

Question 10

What test involving working and episodic memory shows prefrontal influence for working memory in humans?

Answer 10

Controls, temporal lobe lesions with little hippocampal or much hippocampal involvement, and frontal lobe lesions patients saw 12 pictures and had to perform a series of task. One task involved just touch all of them without repetition in any order, but the task that seems to matter for the lecture involved touching one on one page, then turning the page where the pictures were presented in a new order and having to touch a new picture, and so-on.

Controls made about 8 errors, but those with left hippocampal or left PFC lesions made closer to 15. Those with right hippocampal, left nonhippocampal or right PFC made more like 10-12. Those with Right nonhippocampal made 8.

Question 11

What is a problem with delayed matching tests?

Answer 11

Many of them don’t have matching non-samples, so the first match is the sample.

An ABBA test was designed that contained matching non-samples, some back-to-back. He saw that monkeys were responding to the second non-match as a match. This showed that recency was affecting their decisions.

It’s called ABBA because B represents the repetition of non-sample objects.

Question 12

What does the prefrontal cortex have to do during a delay sample to match task?

Answer 12

Monkeys had to discriminate among the stimuli, maintain a memory of the sample stimulus during the delay periods, and evaluate whether a test stimulus matched the sample presented earlier in the trial. PF cells have properties consistent with a role in all three of these operations.

Question 13

What is true about the first delay after a sample in a delay sample to match task?

Answer 13

Half of the cells in PF showed heightened activity during the delay after the sample and, for many of these cells, the magnitude of delay activity was selective for different samples

Question 14

What shows that passive familiarity and working memory are not both prefrontal tasks?

Answer 14

Lesions prefrontal monkeys failed on tests involving working memory but not passive familiarity. Monkeys were show three objects and had to choose one. Then a curtain when down and the monkey saw two of the objects again. He had to choose the object he didn’t choose the first time. Monkeys failed here.

Another version introduced a previously unseen item. Monkeys with prefrontal lesions did fine here because their recognition memory is fine. They knew which object was unfamiliar.

Monkeys with premotor lesions were also tested and did fine.

Question 15

What is true about IT cortex and working memory?

Answer 15

Thus, although the presence of delay activity
after the sample in IT cortex may serve as a sign, or marker, of biasing inputs from PF cortex, its function at present remains unclear.

Question 16

What is true about PF and IT together in working memory?

Answer 16

The results suggest that PF cortex plays a primary role in working memory tasks and
may be a source of feedback inputs to IT cortex, biasing activity in favor of behaviorally relevant stimuli.

Question 17

What is happening with cell suppression and activation during the delay sample to match task?

Answer 17

Some cells in both IT and PF are being suppressed by repetition regardless of whether or not the stimuli are behaviorally relevant. Others are only exciting to the match stimulus

Question 18

Some PF neurons increase in firing across a series of intervening stimuli and delays. Why?

Answer 18

Climbing activity suggests coding of a future event or action that the monkey expects to occur. This type of memory often is referred
to as “prospective memory,” and the animal behavior literature contains abundant evidence for it (see Roitblat, 1993).

Question 19

What is true about enhancement and suppression in the DMS task?

Answer 19

In both IT and PF cortex, match enhancement occurs only for the stimulus that matches the sample, whereas match suppression occurs for any stimulus repetition in the sequence, even if behaviorally irrelevant. In our ABBA
version of DMS, for example, match enhancement occurs only for the matching A stimulus, whereas match-suppression occurs
equally for the matching A and the irrelevant “repeated nonmatch,” B. Distribution of indices showing the strength of the matchenhancement effect (A) and match-suppression effect (B) in PF cortex and
IT cortex. The index is the absolute value of the difference between match and nonmatch responses divided by their sum. Thus, match enhancement, most prevalent in PF
cortex, appears to contribute to active, or working, memory, whereas match suppression, most prevalent in IT cortex, may contribute to the automatic detection of stimulus repetitions.

Question 20

Explain the what, where gradient.

Answer 20

Only 10% of neurons were encoding what, 40% where and the two types intermingle.

It may be a gradient situation where “where” is dorsal with parietal inputs and what isventral with inferotemporal inputs.

Question 21

Explain tonic and phasic.

Answer 21

Tonic in physiology refers to a physiological response which is slow and may be graded. This term is typically used in opposition to a fast response. For instance, tonic muscles are contrasted by the more typical and much faster twitch muscles, while tonic sensory nerve endings are contrasted to the much faster phasic sensory nerve endings.

Question 22

What do fMRI studies of humans show about working memory? How was it different to non-prefrontal areas?

Answer 22

Prefrontal cortex shows tonic activation during epochs of working memory (when the images appear).

Visual responses in otehr areas showed a phasic response.

Question 23

What is true about Moody’s neural network during its delay period?

Answer 23

Hidden units were active and the units active for location were different depending on what location was being remembered.

Question 24

What study shows that working memory neurons may not be domain specific?

Answer 24

A study that involved seeing an object, holding it in memory, then seeing that object with several other objects and having to remember where it is, then making a saccade to its location.

The same neuron fired for both what and where.

Question 25

Explain the what, where gradient.

Answer 25

Only 10% of neurons were encoding what, 40% where and the two types intermingle.

It may be a gradient situation where “where” is dorsal with parietal inputs and what isventral with inferotemporal inputs.

Question 26

Explain the attractor net theory of working memory.

Answer 26

The PFC could have settable firing rates, but its more likely that it contains or is part of an attractor net.

ie. there are two attractor states. In one state, active cells suppress other cells. Active, silent or silent, active.

I think this means that any firing will cause a jump to one state. If the network is put in the region of it, it will remain in it.

Question 27

How does Moody’s recurrent neural network work?

Answer 27

It can solve the DMS problem by having “axons” from cells active for the match feedback to cells not previously activated for the match and through a hidden unit feed to the cells again in a circuit.

Question 28

What did Moody’s model show about attractor states?

Answer 28

There were exactly 8 of them and lesioning reduced the number. White dots were flashed to locations and different locations activate different attractor networks.