The prefrontal cortex in sleep

Experimental data indicate a role for the prefrontal cortex in mediating normal sleep physiology, dreaming and sleep-deprivation phenomena. During nonrandom-eye-movement (NREM) sleep, frontal cortical activity is characterized by the highest voltage and the slowest brain waves compared to other cortical regions. The differences between the self-awareness experienced in waking and its diminution in dreaming can be explained by deactivation of the dorsolateral prefrontal cortex during REM sleep. Here, we propose that this deactivation results from a direct inhibition of the dorsolateral prefrontal cortical neurons by acetylcholine, the release of which is enhanced during REM sleep. Sleep deprivation influences frontal executive functions in particular, which further emphasizes the sensitivity of the prefrontal cortex to sleep.     

Memory conformity: can eyewitnesses influence each other's memories for an event?

The current study investigated memory conformity effects between individuals who witness and then discuss a criminal event, employing a novel procedure whereby each member of a dyad watches a different video of the same event. Each video contained unique items that were thus seen only by one witness. Dyads in one condition were encouraged to discuss the event before each witness (individually) performed a recall test, while in a control condition dyads were not allowed to discuss the event prior to recall. A significant proportion (71%) of witnesses who had discussed the event went on to mistakenly recall items acquired during the discussion. There were no age‐related differences in susceptibility to these memory conformity effects in younger (18–30 years) as compared to older (60–80 years) participants. Possible social and cognitive mechanisms underlying the distortions of memory due to conformity are discussed. Copyright © 2003 John Wiley & Sons, Ltd.     

Temporal Contiguity and Contingency Judgments: A Pavlovian Analogue

The two experiments reported examine the role of temporal contiguity on judgments of contingency in a human analogue of the Pavlovian task. The data show that the effect of the actual delay on contingency judgment depends on the observer's expectation regarding the delay. For a fixed contingency between the cue and the outcome, ratings of the contingency are higher when the actual delay is congruent with the observer's expectation than when it is incongruent. We argue that our data can be understood within the context of the temporal coding hypothesis.     

Visual inertia of rotating 3-D objects

Five experiments were designed to determine whether a rotating, transparent 3-D cloud of dots (simulated sphere) could influence the perceived direction of rotation of a subsequent sphere. Experiment 1 established conditions under which the direction of rotation of a virtual sphere was perceived unambiguously. When a near-far luminance difference and perspective depth cues were present, observers consistently saw the sphere rotate in the intended direction. In Experiment 2, a near-far luminance difference was used to create an unambiguous rotation sequence that was followed by a directionally ambiguous rotation sequence that lacked both the near-far luminance cue and the perspective cue. Observers consistently saw the second sequence as rotating in the same direction as the first, indicating the presence of 3-D visual inertia. Experiment 3 showed that 3-D visual inertia was sufficiently powerful to bias the perceived direction of a rotation sequence made unambiguous by a near-far luminance cue. Experiment 5 showed that 3-D visual inertia could be obtained using an occlusion depth cue to create an unambiguous inertia-inducing sequence. Finally, Experiments 2, 4, and 5 all revealed a fast-decay phase of inertia that lasted for approximately 800 msec, followed by an asymptotic phase that lasted for periods as long as 1,600 msec. The implications of these findings are examined with respect to motion mechanisms of 3-D visual inertia.