It's about time: why right spatial neglect is mild

Abstract

Neglect of right visual space arising from left hemisphere lesions is typically milder than the converse circumstance (left neglect from right hemisphere lesions). Recent theories of left neglect suggest that non-spatial deficits play a crucial role in the disorder. One potential explanation for the more mild nature of right spatial neglect would suggest that these patients may not demonstrate the same impairments in non-spatial functions that are evident in left spatial neglect. We examined this hypothesis in one patient (HW) with a posterior cerebral artery stroke affecting temporal and occipital cortex and the posterior thalamus.

Patient HW demonstrated mild right spatial neglect on line bisection and figure copying tasks. We then tested his perception of time on two tasks. The patient first had to estimate the duration (to the nearest second) of visual events presented for intervals of 5, 15, 30, or 60 seconds. Left spatial neglect patients demonstrate a characteristic performance on this task such that they massively underestimate all durations. The second task provided an auditory analogue to the visual time estimation task with the patient asked to estimate the duration of newspaper stories read aloud for durations equal to those used in the visual task. HW demonstrated normal estimates of visual events. For the auditory task he consistently overestimated durations and demonstrated a far greater degree of variance. We suggest that right spatial neglect is mild due to the absence of non-spatial deficits including the temporal perception of visual events.

Footnotes

 This work was supported by the Heart and Stroke Foundation of Ontario (HSFO).