COMPARATIVE EFFECTS OF AGING AND DEMENTIA OF THE ALZHEIMER-TYPE ON ORIENTATION OF VISUAL-ATTENTION

Age-related changes and the effects of dementia of the Alzheimer type (DAT) were investigated during a visual orienting attention task in wh ich attention was pre-cued to one or other hemifields. Central cues we re either valid, neutral, invalid or NoGo (inhibitory). The response t ime cost-benefit analysis showed a decreased benefit after valid cuein g in the old compared with the young group with no change in the cost of invalid cueing. The older group were also slower over all cue types . These results suggest there is an age-related reduced ability to cov ertly orient attention in a visual hemifield before target onset. In c ontrast, the DAT group showed an increased response time benefit and s howed a trend for a decreased cost in response time compared with cont rols. This was due to slowest response times after neutral cues. They also made significantly more response errors particularly following ne utral cueing, and were less able to inhibit responses on NoGo trials t han controls. The increased benefit and reduced cost found in the DAT group was interpreted as an impairment in dividing attention between l eft and right target locations.