Cortical involvement in visual scan in the monkey

Abstract

Monkeys performed a visual search task for food reward. Green square targets were embedded in 3 x 3 arrays of colored forms. In distinct-feature arrays, all nontarget stimuli were red diamonds, whereas in shared-feature arrays, some nontarget stimuli shared either form (red square) or color (green diamond) with the target. Reaction time was slower for shared-feature arrays and linearly related to the number of shared-feature distractors. Errors were more common in sharedfeature arrays, and shared-feature distractors were mistaken for targets more frequently than distinct-feature distractors. Event-related local field potentials were recorded from implanted transcortical electrodes. Significant task-related differences were obtained from association cortex, but not from projection cortex. Results are discussed in terms of the relative contribution of inferotemporal, dorsolateral frontal, and parietal cortex to feature-driven visual scan.Some 30 years ago, J. Z. Young (1962) developed the theme that the primary sensory projection systems of the brain have evolved to map the sensory environment, whereas the more intrinsically connected "association" cortex performs abstract computations on the mapping functions. In discussing this paper, one of us (Pribram, 1962) presented evidence that such abstract computations were composed by sampling the maps in a top-down fashion. More recently, a great deal of interest has been generated by Schneider and Shiffrin's (for a review, see Schneider, Dumais, & Shiffrin, 1984) observations of the conditions that predispose humans toward automatic as opposed to those which predispose them toward controlled processing of sensory input. Automatic processing was considered to operate simultaneously on maps of the input; controlled processing was considered to entail scans (searches) of the input.Additional experiments by Efron have called attention to the fact that a variety of hitherto conflicting or unexplained observations-especially with regard to differences in hemispheric function-can be understood in terms of the order in which sensory input is sampled, or scanned (for a review, see Efron, 1990). Scanning wasThe authors are indebted to Sharon E. Hendricks for collection and analysis of data reported in Experiment I, and to Margaret J. Harrington, Stephen D. Cutcomb, and Ronald M. Ruff for assistance in surgery, computer programming, and data collection in Experiment 2. Funding for this research was provided by grants from the Natural Sciences and Engineering Research Council of Canada to R.B., and from NIHINIMH to K.H.P. Correspondence should be addressed to K. H. Pribram, Center for Brain Research and Informational Sciences, Radford University, Box 6977, Radford, VA 24142. shown to occur during a postexposure period and thus to be independent of eye movement. Some central brain process, shown to be influenced by experience, was inferred to be responsible.In monkeys, several experiments have been carried out in our laboratory to investigate whether indeed the sensory project...

Does Dyslexia Develop from Learning the Alphabet in the Wrong Hemisphere? A Cognitive Neuroscience Analysis

“…Moreover there is a convergence of PET evidence indicating that BA45 is involved in transforming sublexical orthographic input into phonological output codes (Fiez, Balota, Raichle, & Peterson, 1999;Hagoort et al, 1999). It is also noteworthy that Bolster and Pribram (1993) postulated an analogous internal visual scanning processing involving parietal, frontal, and temporal cortices in explaining ERP feature-processing research with monkeys. As well, brain stimulation mapping of human subjects has implicated all three of these areas in phonemic identification (Ojemann & Mateer, 1979).…”

Guidance of Eye Movements During Visual Conjunction Search: Local and Global Contextual Effects on Target Discriminability

“…The monkeys were required to foveate a target stimulus to receive a liquid reward but were granted a generous length of time so that they could freely visit whichever stimuli they wished to examine. Here we report on the behavioral performance of these animals as it relates to three specific issues that were not resolved in the previous visual conjunction search studies conducted with monkeys (Bichot and Schall 1999;Bolster and Pribram 1993;Buracas and Albright 1999;Motter and Belky 1998b).…”

“…We first asked whether the visual search strategies of monkeys are shaped by the composition of the stimuli within a search display. The original study of Bolster and Pribram (1993) showed that the latency of manual responses during conjunction search increases with the number of distractors sharing a feature with the target, suggesting only indirectly that visual strategies changed with display composition. Since then, the distractor-ratio effect has been examined in only one monkey and with search displays of varying number of stimuli (Buracas and Albright 1999).…”

“…Generally, both monkeys and humans bias their search by visiting distractors sharing one particular feature with the target (Bichot and Schall 1999;Buracas and Albright 1999;Motter and Belky 1998b;Shen et al 2003; see also Bolster and Pribram 1993;Zohary and Hochstein 1989), and they rarely fixate distractors that share no feature with the target (Bichot and Schall 1999;Findlay 1997). These studies suggest that different distractors have different values, and we wished to determine whether the variability in conjunction search performance could be accounted for by the exact arrangement of the stimuli in a search display.…”

Saccade target selection in macaque during feature and conjunction visual search

“…Preliminary studies have measured reaction time as a function of set size (Dürsteler & von der Heydt, 1992;Buračas & Albright, 1997). A study by Bolster and Pribram (1993) in which monkeys reached toward the conjunction target revealed a very steep slope of 60 ms0item, and there were more errors to distractors that shared a target property than to distractors that shared none. However, the response latencies in this study were quite long and, unfortunately, saccades were not monitored.…”