J Neurosci. 2009 March 11; 29(10): 3073–3082. doi:10.1523/JNEUROSCI.3452-08.2009.
The effects of rehearsal on the functional neuroanatomy of
episodic autobiographical and semantic remembering: an fMRI
study
Eva Svoboda1 and Brian Levine1
1Rotman Research Institute, Baycrest, 3560 Bathurst Street, Toronto, Ontario, M6A 2E1
Abstract
This study examined the effects of rehearsal on the neural substrates supporting episodic
autobiographical and semantic memory. Stimuli were collected prospectively using audio recordings,
thereby bringing under experimental control ecologically-valid, naturalistic autobiographical stimuli.
Participants documented both autobiographical and semantic stimuli over a period of 6 to 8 months,
followed by a rehearsal manipulation during the three days preceding scanning. During fMRI
scanning participants were exposed to recordings that they were hearing for the first, second or eighth
time. Rehearsal increased the rated vividness with which information was remembered, particularly
for autobiographical events. Neuroimaging findings revealed rehearsal-related suppression of
activation in regions supporting episodic autobiographical and semantic memory. Episodic
autobiographical and semantic memory produced distinctly different patterns of regional activation
that held even after eight repetitions. Region of interest analyses further indicated a functional
anatomical dissociation in response to rehearsal and memory conditions. These findings revealed
that the hippocampus was specifically engaged by episodic autobiographical memory, whereas both
memory conditions engaged the parahippocampal cortex. Our data suggest that when retrieval cues
are potent enough to engage a vivid episodic recollection, the episodic/semantic dissociation within
medial temporal lobe structures endure even with multiple stimulus repetitions. These findings
support the Multiple Trace Theory (MTT) which predicts that the hippocampus is engaged in the
retrieval of rich episodic recollection regardless of repeated reactivation such as that occurring with
the passage of time.
Current Opinion in Neurobiology 2008, 18:131–136:
Human time perception and its illusions
David M Eagleman1,2
Why does a clock sometimes appear stopped? Is it possible to
perceive the world in slow motion during a car accident? Can
action and effect be reversed? Time perception is surprisingly
prone to measurable distortions and illusions. The past few
years have introduced remarkable progress in identifying and
quantifying temporal illusions of duration, temporal order, and
simultaneity. For example, perceived durations can be
distorted by saccades, by an oddball in a sequence, or by
stimulus complexity or magnitude. Temporal order judgments
of actions and sensations can be reversed by the exposure to
delayed motor consequences, and simultaneity judgments can
be manipulated by repeated exposure to nonsimultaneous
stimuli. The confederacy of recently discovered illusions points
to the underlying neural mechanisms of time perception.
Addresses
1 Department of Neuroscience, Baylor College of Medicine, 1 Baylor
Plaza, Houston, TX 77030, United States
2 Department of Psychiatry, Baylor College of Medicine, 1 Baylor Plaza,
Houston, TX 77030, United States
Corresponding author: Eagleman, David M (
eagleman@bcm.edu)
).