The Journal of Neuroscience, September 15, 1998, 18(18):7426-7435
Where and When to Pay Attention: The Neural Systems for Directing
Attention to Spatial Locations and to Time Intervals as Revealed by
Both PET and fMRI
Jennifer T.
Coull1 and
Anna C.
Nobre1, 2
1 Functional Imaging Laboratory, Wellcome Department of
Cognitive Neurology, Institute of Neurology, London WC1N 3BG, United
Kingdom, and 2 University of Oxford, Department of
Experimental Psychology, Oxford OX1 3UD, United Kingdom
Although attention is distributed across time as well as space, the
temporal allocation of attention has been less well researched than its
spatial counterpart. A temporal analog of the covert spatial
orientation task [Posner MI, Snyder CRR, Davidson BJ (1980) Attention
and the detection of signals. J Exp Psychol Gen 109:160-174] was
developed to compare the neural systems involved in directing attention
to spatial locations versus time intervals. We asked whether there
exists a general system for allocating attentional resources,
independent of stimulus dimension, or whether functionally specialized
brain regions are recruited for directing attention toward spatial
versus temporal aspects of the environment. We measured brain activity
in seven healthy volunteers by using positron emission tomography (PET)
and in eight healthy volunteers by using functional magnetic resonance
imaging (fMRI). The task manipulated cued attention to spatial
locations (S) and temporal intervals (T) in a factorial design.
Symbolic central cues oriented subjects toward S only (left or right),
toward T only (300 msec or 1500 msec), toward both S and T
simultaneously, or provided no information regarding S or T. Subjects
also were scanned during a resting baseline condition.
Behavioral data showed benefits and costs for performance during
temporal attention similar to those established for spatial attention.
Brain-imaging data revealed a partial overlap between neural systems
involved in the performance of spatial versus temporal orientation of
attention tasks. Additionally, hemispheric asymmetries revealed
preferential right and left parietal activation for spatial and
temporal attention, respectively. Parietal cortex was activated
bilaterally by attending to both dimensions simultaneously. This is the
first direct comparison of the neural correlates of attending to
spatial versus temporal cues.
Key words:
attention; space; time; orienting; parietal; lateralization; imaging
Copyright © 1998 Society for Neuroscience 0270-6474/98/18187426-10$05.00/0