PSYCH 4320 / COGST 4310 / BioNB 4330

Consciousness and Free Will

Imagine

  Week 10: time

Week 10: time

  • Episodic and prospective memory —

    • in scrub jays
    • in people
  • The "dark network"
  • The personal time machine

a Borgesian digression


In China, the dream of Chuang Tzu is proverbial; let us imagine that one of its almost infinite readers dreams he is a butterfly and then that he is Chuang Tzu. Let us imagine that, by a not impossible chance, this dream repeats exactly the dream of the master. Having postulated such an identity, we may well ask: Are not those coinciding moments identical? Is not one single repeated term enough to disrupt and confound the history of the world, to reveal that there is no such history?

— from The New Refutation of Time by Jorge Luis Borges

a Borgesian digression


In China, the dream of Chuang Tzu is proverbial; let us imagine that one of its almost infinite readers dreams he is a butterfly and then that he is Chuang Tzu. Let us imagine that, by a not impossible chance, this dream repeats exactly the dream of the master. Having postulated such an identity, we may well ask: Are not those coinciding moments identical? Is not one single repeated term enough to disrupt and confound the history of the world, to reveal that there is no such history?

— from The New Refutation of Time by Jorge Luis Borges
In the fall of 1940, Feynman received a telephone call from John Wheeler [Feynman's thesis advisor] at the Graduate College in Princeton, in which he [Wheeler] said that he knew why all electrons have the same charge and the same mass. "Why?" asked Feynman, and Wheeler replied, "Because they are all one and the same electron." — Jagdish Mehra, quoted here

a Borgesian digression: the dynamical systems perspective


Two dynamical systems comprised of identical elements do not collapse into one even if they happen to pass through identical states.

time and memory


"The first notion to get rid of is that memory is primarily or literally reduplicative, or reproductive. In a world of constantly changing environment, literal recall is extraordinarily unimportant. If we consider evidence rather than supposition, memory appears to be far more decisively an affair of construction rather than one of mere reproduction."

time and memory


"The first notion to get rid of is that memory is primarily or literally reduplicative, or reproductive. In a world of constantly changing environment, literal recall is extraordinarily unimportant. If we consider evidence rather than supposition, memory appears to be far more decisively an affair of construction rather than one of mere reproduction."

Bartlett (1932)

reduced false recognition in dementia and amnesia (Schacter & Addis, 2007)


"... 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.

episodic memory in jays (Clayton et al., 2003)


And now to something completely different quite similar:

a western scrub jay caching wax worms.

testing episodic/prospective memory in jays

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.

[In the illustration, the two conditions are switched around]

testing episodic/prospective memory in jays

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.

testing episodic/prospective memory in jays


"Scrub jays that had experience of stealing another bird's caches subsequently re-cached food in new cache sites during recovery trials, but only when they had been observed caching.

Conspecifics without this experience did not do so, even though they had observed other jays caching."


"As re-caching does not depend on the [current] presence of the potential thief, the scrub jays must relate information about their previous experience as a thief to the possibility of future stealing by another bird, and modify their caching strategy accordingly.

The next important step is to establish whether jays are sensitive to a future motivational state as opposed to the current one."

'planning for breakfast' experiment (Raby et al., 2007)

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?

'breakfast choice' experiment

"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.

[Conditioning account predicts that the jays would cache a particular food in the compartment previously associated with that food.]

'breakfast choice' experiment: conclusion


Raby et al. conclude:

"In the absence of language, there is no knowing whether this reflects episodic future thinking, in which the bird is projecting itself into tomorrow morning's situation, or semantic future thinking, in which the jay takes prospective action, but without personal mental time travel into the future. However, in either case it shows that these birds must have the capability to plan for a future motivational state over a timescale stretching at least into tomorrow."

forms of self-projection (Buckner & Carroll, 2007)

Self-projection relies on a personal, mental simulation of another time, place or perspective (first-person or third-person) —
(a) Remembering: simulating the past, such as the picnic earlier.
(b) Prospection: simulating a possible future event, such as cleaning up the mess.
(c) Theory of mind: conceiving another person's perspective, such as the mental state of the person about to be recruited to help clean.
(d) Navigation: simulating another view or mapping the environment, such as a mental map of the world that surrounds the picnic area, including the location of the nearest trash bin.

All these abilities depend on a shift from the present perspective to a simulated model of an alternative world. All use specific past instances from memory as constraints in forming the mental simulations. These forms of self-projection might rely on a common brain network.

brain activation during self-projection

There is a remarkable correspondence in activation during remembering (a), prospection (b) and theory-of-mind (c) tasks.

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.

the brain in the "default mode"


The brain activity pattern associated with the default mode, illustrating those regions that are most active when people passively think to themselves, as compared with a range of active tasks that demand external attention and decision processes.

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.

at rest, but active (Raichle, 2006)


The highly organized nature of intrinsic brain activity manifests itself correlated spontaneous fluctuations in the fMRI signal. This figure shows regions of positive correlation with seed voxels drawn from areas known to increase activity during responses to controlled stimuli; and regions of negative correlations with seeds drawn from areas that decrease activity under the same conditions.

remembering the past and imagining the future (Schacter & Addis, 2007)

Comparing true and false recognition in a prototype paradigm.

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.

construction and elaboration of past and future

Common and distinct regions engaged by the construction and elaboration of past and future events.

Comparable activity: left hippocampus and right occipital gyrus (BA 19). Differentially more activity for future events: right frontal pole and hippocampus.

The elaboration phase was marked by "striking" overlap between past and future events, including left hippocampus, left temporal pole, bilateral parietal lobule (BA 39) and retrosplenial cortex.

construction and elaboration of past and future

Commonalities in the medial left prefrontal and parietal regions engaged when (a) remembering the past and (b) imagining the future.

Similarities were also evident in 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 construction of past and future events; it only emerged during the elaboration of these events (shown here, relative to elaboration phase of a semantic and an imagery control task).


[Recall the central role of the hippocampus in Merker's proposed brain basis for personal/"narrative" memory, Lecture 6.]

neural correlates of envisioning the future (Szpunar et al., 2007): it is personal

(A-D) 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) A statistically indistinguishable pattern of activity 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.

mind wandering = unhappiness (Killingsworth & Gilbert, 2010)


Mean happiness reported during each activity (top) and while mind wandering to unpleasant topics, neutral topics, pleasant topics or not mind wandering (bottom).
Dashed line: mean across all samples.
Bubble area: frequency of occurrence.

The largest bubble ("not mind wandering") corresponds to 53.1% of the samples, and the smallest bubble ("praying/worshipping/meditating") corresponds to 0.1% of the samples.

[But what about the link between depression and being stuck in the present?]

[See also my blog post Gateway Drugs for the Masses: "The practice of living the moment may impede individual development and social progress. Think about it. Now."]

time travel in the brain

When we appear to be doing nothing, we are clearly doing something. But what? The answer, it seems, is time travel.

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.

— D. T. Gilbert & R. Buckner
Time travel in the brain
Time (Friday, Jan. 19, 2007)