Lecture 12: time
- Young vs. old
- Episodic and prospective memory —
- in scrub jays;
- in rats;
- in people.
- The "dark network"
- Time travel
In each pair, the ads are identical except for
Older participants preferred the ads featuring the emotion-related slogans. They also remembered these slogans and the products associated with them better than they did the slogans about exploration and knowledge.
When older participants were asked to imagine an expanded future before choosing, they made choices similar to those of younger participants.
slide 4
The percentage of signal change in amygdala activation in response to emotionally positive, emotionally neutral, and emotionally negative images.
Younger people show significantly increased activation in response to positive and negative images. Older people show increased activation only in response to positive images.
"This motivational shift occurs with age but also appears in other contexts (for example, geographical relocations, illnesses, and war) that limit subjective future time."
slide 5
"... memory appears to be far more decisively an affair of construction rather than one of mere reproduction." — Bartlett (1932)
... hence the patterns of memory errors.
slide 8
And now to something completely different quite similar:
slide 9
The procedure used to test episodic memory in jays.
Birds in the "degrade" group cache perishable wax worms and non-perishable peanuts, which they are allowed to recover later. If a short time has elapsed, the birds should prefer to recover the worms; if a long time has elapsed, they should prefer to recover the peanuts.
slide 10
The procedure used to test whether the jays can adjust their caching strategy to minimize potential plundering by other birds.
On some trials, the subject caches while observed by a conspecific; on others, the subject caches in private. Recovery is always allowed to happen in private.
slide 11
Compartmental layout used for the 'planning for breakfast' experiments.
The position of caching trays is shown in compartments A and C, and of the food bowl(s) in compartment B. Dotted lines represent the compartmental divisions, although during caching no dividers were in place.
In experiment 1, the birds anticipated their hunger the next morning by storing significantly more pine nuts in the caching tray in the 'no-breakfast' compartment than in the 'breakfast' compartment.
Was differential caching due to a propensity to cache in places associated with hunger?
slide 13
"SAME": peanuts cached in the "peanuts-for-breakfast" compartment; kibble cached in the "kibble-for-breakfast" compartment. "DIFFERENT": the other way round.
In accord with the future planning account, and contrary to the conditioning account, at test the birds stored significantly more of the "different" food than the "same" food in each compartment relative to the amount of that food that they stored in the other compartment.
"In the absence of language, there is no knowing whether this reflects
slide 14
Self-projection relies on a personal, mental simulation of another time, place or perspective (first-person or third-person).
slide 15
There is a remarkable correspondence in activation during
Convergence also extends to lateral parietal regions (not shown), located within the inferior parietal lobule near the temporo-parietal junction.
(d) Cortical regions that functionally correlated with the medial temporal lobe (MTL). The MTL network overlaps the regions that are recruited during the multiple forms of self-projection.
slide 16
The brain activity pattern associated with the
Note the remarkable similarity between the default regions and those engaged during self-projection and also the similarity to those regions that are functionally correlated with the medial temporal lobe memory system.
slide 17
The highly organized nature of intrinsic brain activity manifests itself correlated spontaneous fluctuations in the fMRI signal. Positive correlations reside in areas known to increase activity during responses to controlled stimuli; negative correlations reside in areas that decrease activity under the same conditions.
slide 18
Tolman and Gleitman's famous behavioral experiment on latent learning using a T-maze.
The maze contained two arms: for illustration, the end chamber of one arm is darkened and the end chamber of the other arm is light. (a) Initially, the rat explores all parts of the T-maze. (b) The rat is removed and placed in the darkened chamber where it experiences a series of shocks. (c) When placed back in the T-maze, the rat chooses the safe path. The rat probably represents the decision choice, in some manner, in advance of the action, which raises the possibility of a proto-form of experience projection.
Comparing true and false recognition in a
Several regions previously implicated in true recognition — hippocampus, lateral parietal cortex, and dorsolateral and inferior prefrontal cortex — showed significant and comparable levels of activity during false recognition of new related shapes (i.e. prototypes) and true recognition of studied shapes, compared with correct rejections of new unrelated shapes. BA, Brodmann area; CR, correct rejection; FA, false alarm.
slide 20
Common and distinct regions engaged by the
Comparable activity: left hippocampus and right occipital gyrus (BA 19).
Differentially more activity for future events: right frontal pole and hippocampus.
The
slide 21
Sagittal slice illustrating the striking commonalities in the medial left prefrontal and parietal regions engaged when (a) remembering the past and (b) imagining the future.
These marked similarities of activation were also evident in areas of the medial temporal lobe (left hippocampus, bilateral parahippocampal gyrus) and lateral cortex (left temporal pole and left bilateral inferior parietal cortex).
The common activity was not present during the
[Recall the central role of the hippocampus in Merker's proposed brain basis for personal memory, Lecture 6.]
slide 22
(A-D) Percent signal change for representative regions showing a significant interaction such that imagining of future events (SF) led to greater activation than did recollecting oneself in the past (SR). Both self-related tasks also led to greater activity than a control task involving imagery of another person participating in similar events (CI).
(E-H) Percent signal change for selected regions showing a statistically indistinguishable pattern of activity across time while subjects envisioned their personal future (SF) and recollected the past (SR) in response to a series of event cues (e.g., Birthday). Imagining a familiar individual in similar scenarios (CI) resulted in a pattern of activity different from both the past and future tasks.
slide 23
Regions of the default network exhibiting significantly greater activity during practiced blocks (red) relative to novel blocks (blue) at a threshold of P < 0.001, number of voxels (k) = 10. Graphs depict the mean signal change across all participants.
slide 24
Regions that exhibited a significant positive relation (r > 0.50, P < 0.05) between the frequency of mindwandering and the change in BOLD signal observed when people performed practiced vs. novel blocks.
BOLD difference scores (practiced — novel) are plotted against their standardized IPI daydreaming score.
slide 25
The dark network [the default network, comprised by regions that are active when the brain is not engaged in any particular task] allows us to visit the future, but not just any future. When we contemplate futures that don't include us ... the dark network is quiet. Only when we move ourselves through time does it come alive.
|
|
|
Lecture 12 Last modified on Mon Apr 16 13:55:33 2007 |
|