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Increased fMRI activation of anterior cingulate to infrequent compared to frequent stimuli in an auditory oddball task
ABSTRACTS
Increased fMRI Activation of Anterior Cingulate to Infrequent C o m p a r e d to Frequent Stimuli in an Auditory Oddball Task V . M e n o n , K . O. L i m , J. M . F o r d a n d A. P f e f f e r b a u m Department of Psychiatry $J Behavioral Sciences Stanford University School of Medicine and VA Palo Alto Health Care System Event-related potentials (ERPs) to the auditory oddball task have been investigated extensively in the last three decades. Recently, PET (Nenov et al, 1994) and SPECT (Ebmeier et al, 1995) studies have indicated activation of the anterior cingulate during the oddball task when compared to a resting baseline. In the present study, functional MRI was used to investigate activation of the anterior cingulate by directly comparing the activation elicited by the target infrequent tone to that elicted by the non-target frequent tone. Methods Four right handed subjects participated in the study. The stimuli were eighty 1000Hz and twenty 2000Hz tones presented randomly with an inter-stimulus interval of 8s. Subjects pressed a response ball to infrequent tones. Axial functional images were acquired every 4s at 12 locations with a slice thickness of 7ram. Images were normalized to Talaraich coordinates and analyzed using Statistical Parametric Mapping (Friston et al, 1995). Foci of activation were detected using a reference function, consisting of +1 for the infrequent tone and -1 for the frequent tone, convolved with the haemodynamic response. Results reported here are for Z > 2.3 (p < 0.05, uncorrected). Results Increased activation of the anterior cingulate to infrequent tones was detected in all four subjects. Fig. 1 (left) shows activation foci from one of the subjects (BA 24, Talaraich coordinates: -2, 6, 30). Fig. 1 (right) shows that the fMRI time series at this location is covariant with the infrequent tone. In the remaining three subjects, the activation foci in the anterior cingulate were BA 24 (-4, 0, 34), BA 24/32 (-2, 16, 32), and BA 32 (-4, 4, 43).
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fMRI activation infrequent tone
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Figure 1: Anterior Cingulate activation (Left) and fMRI time series (Right) to infrequent tones. Conclusions The results demonstrate that activation of the anterior cingulate is greater to the infrequent than the frequent tones in the auditory oddball task. The results suggest that the activation of the anterior cingulate is not merely related to enhanced generalized attention during the task, and may have implications for understanding the neural substrates of the P300 component of the ERP.
$234
Increased fMRI Activation of Anterior Cingulate to Infrequent C o m p a r e d to Frequent Stimuli in an Auditory Oddball Task V . M e n o n , K . O. L i m , J. M . F o r d a n d A. P f e f f e r b a u m Department of Psychiatry $J Behavioral Sciences Stanford University School of Medicine and VA Palo Alto Health Care System Event-related potentials (ERPs) to the auditory oddball task have been investigated extensively in the last three decades. Recently, PET (Nenov et al, 1994) and SPECT (Ebmeier et al, 1995) studies have indicated activation of the anterior cingulate during the oddball task when compared to a resting baseline. In the present study, functional MRI was used to investigate activation of the anterior cingulate by directly comparing the activation elicited by the target infrequent tone to that elicted by the non-target frequent tone. Methods Four right handed subjects participated in the study. The stimuli were eighty 1000Hz and twenty 2000Hz tones presented randomly with an inter-stimulus interval of 8s. Subjects pressed a response ball to infrequent tones. Axial functional images were acquired every 4s at 12 locations with a slice thickness of 7ram. Images were normalized to Talaraich coordinates and analyzed using Statistical Parametric Mapping (Friston et al, 1995). Foci of activation were detected using a reference function, consisting of +1 for the infrequent tone and -1 for the frequent tone, convolved with the haemodynamic response. Results reported here are for Z > 2.3 (p < 0.05, uncorrected). Results Increased activation of the anterior cingulate to infrequent tones was detected in all four subjects. Fig. 1 (left) shows activation foci from one of the subjects (BA 24, Talaraich coordinates: -2, 6, 30). Fig. 1 (right) shows that the fMRI time series at this location is covariant with the infrequent tone. In the remaining three subjects, the activation foci in the anterior cingulate were BA 24 (-4, 0, 34), BA 24/32 (-2, 16, 32), and BA 32 (-4, 4, 43).
-- --
-
fMRI activation infrequent tone
'-
~
r
-2 0
50
100
150
200
image
Figure 1: Anterior Cingulate activation (Left) and fMRI time series (Right) to infrequent tones. Conclusions The results demonstrate that activation of the anterior cingulate is greater to the infrequent than the frequent tones in the auditory oddball task. The results suggest that the activation of the anterior cingulate is not merely related to enhanced generalized attention during the task, and may have implications for understanding the neural substrates of the P300 component of the ERP.
$234