WHERE AND WHEN TO PAY ATTENTION - THE NEURAL SYSTEMS FOR DIRECTING ATTENTION TO SPATIAL LOCATIONS AND TO TIME INTERVALS AS REVEALED BY BOTHPET AND FMRI
Jt. Coull et Ac. Nobre, WHERE AND WHEN TO PAY ATTENTION - THE NEURAL SYSTEMS FOR DIRECTING ATTENTION TO SPATIAL LOCATIONS AND TO TIME INTERVALS AS REVEALED BY BOTHPET AND FMRI, The Journal of neuroscience, 18(18), 1998, pp. 7426-7435
Although attention is distributed across time as well as space, the te
mporal allocation of attention has been less well researched than its
spatial counterpart. A temporal analog of the covert spatial orientati
on task [Posner MI, Snyder CRR, Davidson BJ (1980) Attention and the d
etection of signals. J Exp Psychol Gen 109:160-174] was developed to c
ompare the neural systems involved in directing attention to spatial l
ocations versus time intervals. We asked whether there exists a genera
l system for allocating attentional resources, independent of stimulus
dimension, or whether functionally specialized brain regions are recr
uited for directing attention toward spatial versus temporal aspects o
f the environment. We measured brain activity in seven healthy volunte
ers by using positron emission tomography (PET) and in eight healthy v
olunteers by using functional magnetic resonance imaging (fMRI). The t
ask manipulated cued attention to spatial locations (S) and temporal i
ntervals (T) in a factorial design. Symbolic central cues oriented sub
jects toward S only (left or right), toward T only (300 msec or 1500 m
sec), toward both S and T simultaneously, or provided no information r
egarding S or T Subjects also were scanned during a resting baseline c
ondition. Behavioral data showed benefits and costs for performance du
ring temporal attention similar to those established for spatial atten
tion. Brain-imaging data revealed a partial overlap between neural sys
tems involved in the performance of spatial versus temporal orientatio
n of attention tasks. Additionally, hemispheric asymmetries revealed p
referential right and left parietal activation for spatial and tempora
l attention, respectively. Parietal cortex was activated bilaterally b
y attending to both dimensions simultaneously. This is the first direc
t comparison of the neural correlates of attending to spatial versus t
emporal cues.