Visual Saliency and Attention Experimental Investigation of Saliency Processing in ADHD - Initial Findings
Benjamin Cowley, Cognitive Science Unit, Department of Behavioural Sciences
C O G N I T I V E S C I E NC E U N I V E R S I T Y OF H E L S I N K I
UNIVERSITY OF HELSINKI, FINLAND
We investigate the role of visual salience processing in attention deficit disorders (ADHD) using a novel Event-Related Potential (ERP) protocol. Saliency refers to the order of importance attached to visual features by the attention system, making certain features ‘stand out’, with processing time 25-50ms. Task-related or top-down attention can modulate saliency but is much slower, 200ms or more [1].
a strong effect on processing, as expected. In general, amplitudes are higher for Incongruent trials, reflecting that an additional neuronal recruitment is required.
Findings of brain structural alteration in ADHD include significantly smaller volumes in the dorsolateral prefrontal cortex (dPFC) and associated regions: caudate, pallidum, anterior cingulate, and cerebellum [2]. This motivates the study of attentional neural processing in a task requiring top-down redirection of attention. To simulate this, our protocol manipulates the saliency of targets in a choice-response task, testing interference inhibition at the task-response level, and saliency-processing at the pre-attentive level. Here we present initial findings.
RESULTS On behavioural measures, Patients generally performed worse than Controls. In all hit trials, Patients had higher response time means and variability; in all conditions they had lower hit rates and higher false alarms; their d’prime index of sensitivity was lower overall: though it was higher for incongruent trials. This exception might be explained by the EEG results. Of all these comparisons, statistically significant ones are shown in Figure 2. ERPs from four conditions show that Incongruent stimuli had
Figure 1: ERPs from healthy controls and ADHD adults, across four conditions and eight bilateral electrodes (left hemisphere above - odd numbered electrodes; right hemisphere below - even numbered electrodes). Green highlighting shows where groups were different in all four conditions for 50ms timeslices, statistically significant at the p
