S1 (FriAM 1-65) - The Psychonomic Society

Friday Noon Posters 2118–2120
(2118)
Severe Departure From Weber’s Law With Comparisons in the Sensory
Trace Mode. ERVIN R. HAFTER & ANNE-MARIE BONNEL,
University of California, Berkeley (sponsored by Donald A. Riley)—
Increment detection is studied with trials presenting a brief reminder
stimulus, (I), followed by a test stimulus, either (I) or (I + ΔI). Using
this paradigm in an auditory/visual dual task, we have found that the
cost of sharing depends on the memory used for stimulus comparison.
Evidence shows that with I fixed within a block, test stimuli are compared
with standards in long-term memory, and there is a cost of
shared attention indicative of a single, shared attentional resource.
Conversely, when trial-by-trial roving of I forces comparisons in the
sensory trace mode, there is no such cost. The focus here is on the psychophysics
of roving. Unlike in the case of fixed levels, where
Weber’s law holds true, roving produces a severe departure from
Weber’s law that penalizes smaller Is. This indication of a constant additive
noise reflects a cost of holding and comparing stimuli in the
trace mode.
(2119)
The Role of the Hippocampus and LIFGs in Working Memory
Retrieval. ILKE ÖZTEKIN, BRIAN MCELREE, BERNHARD P.
STARESINA, & LILA DAVACHI, New York University—Eventrelated
functional magnetic resonance imaging (fMRI) was used to
isolate regions involved in retrieval from working memory (WM) by
contrasting access to representations maintained in focal attention
with those that required retrieval. Neural activity was measured in two
WM paradigms: a probe recognition task, requiring access to item in-
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formation, and a judgment of recency (JOR) task, requiring access to
temporal order information. In both tasks, a common pattern of activity
emerged in the hippocampus and left inferior frontal gyrus
(LIFG): Activity showed a sharp drop for the most recent item in comparison
with all other items in the list. These results demonstrate the
role of hippocampus and LIFG in WM retrieval. They converge with
timecourse measures in indicating that only the most recently
processed item is maintained in focal attention, and that, unlike other
items in WM, access to this item does not require a retrieval operation.
(2120)
On the Structure of Working Memory. ANDREW R. A. CONWAY,
Princeton University, & JASON M. CHEIN, Temple University—We
used fMRI to explore the relative engagement of the brain’s cognitive
control system by verbal and spatial working memory (WM) and shortterm
memory (STM) span tasks. Subjects performed verbal and spatial
WM span, and STM span, tasks that were developed for compatibility
with fMRI. Each WM span task consisted of a processing and storage
component. Verbal storage was letter memory; verbal processing was
lexical decision; spatial storage was Corsi blocks; and spatial processing
was symmetry judgment. Subjects performed each component
alone, as well as in combination (i.e., as a WM span task). Brain regions
typically associated with cognitive control, including prefrontal, anterior
cingulate, and parietal areas, were most strongly engaged during the
WM span conditions. This pattern was generally consistent across verbal
and spatial tasks. The findings support the view that frontal lobe
function and cognitive control mechanisms mediate the relationship between
WM span and measures of higher cognition.