Information processing in the cerebral hemispheres: Selective hemispheric activation and capacity limitations.

Abstract

Several previous experiments have found that concurrently maintaining verbal information in memory influences visual laterality patterns (e.g., Hellige & Cox, 1976; Kinsbourne, 1975). The present article critically reviews existing experiments and reports five additional experiments designed to identify the mechanisms responsible for such effects. Experiment 1 demonstrates that laterality patterns are not influenced by a concurrent memory task that does not require verbal processing. (The verbal nature of the concurrent task was an important aspect of previous experiments.) Experiments 2 and 3 were designed to determined whether concurrent verbal memory primarily influences very early visuospatial processes or later processes such as those involved in visuospatial memory. In Experiment 2, observers indicated whether two simulteneously presented nonsense forms had the same shape. Observers held 0, 2, 4, or 6 words in memory during each shape judgment trial. Responses were faster when the forms were presented to the left visual field--right hemisphere (LVF-RH) than to the right visual field--left hemisphere (RVF-LH). This effect did not interact with memory set size. In Experiment 3, observers indicated whether either of two simultaneously presented forms was identical to a target form held in memory. Observers held 0, 2, or 6 words in memory on each trial. On same-as-target trials, responses were faster on LVF-RH trials than on RVF-LH trials in the no-word memory condition; this difference was reversed in the two-word and six-word conditions. The combined results of Experiments 2 and 3 suggest that concurrent verbal memory influences stages of processing beyond the initial registration of visuospatial information. Experiments 4 and 5 examined the influence of concurrent verbal memory on verbal laterality tasks. Observers indicated whether two simultaneously presented letters of different cases had the same name. In Experiment 4, different groups of observers held 0, 2, 4, or 6 words in memory on each letter-pair trial. In Experiment 5, memory set size was manipulated within subjects. On the same-pair trials of Experiment 4 and the first session of Experiment 5, responses in the no-memory condition were faster on RVF-LH trials than on LVF-RH trials; this difference was reversed in all of the work memory conditions. This shift is opposite to that found when the laterality task does not require verbal processing and further indicates that concurrent verbal memory influences processing stages beyond those that are common to the form-pair and letter-pair tasks. Neither directness-of-pathway nor attention-gradient laterality models can explain the entire pattern of results from the present experiments. Rather, the results suggest that the left hemisphere functions as a typical limited-capacity information processing system that can be influenced somewhat separately from the right hemisphere system.

An investigation into hemisphere differences in adaptation to contrast

“…If this capacity is occupied by concurrent tasks, then the subject's performance on the test task can be affected (Hellige, Cox, & Litvac, 1979;Moscovitch, 1979). It thus becomes important to consider what else the subject is doing during the experiment which might occupyhis right hemisphere's capacity.…”

Models of anger: contributions from psychophysiology, neuropsychology and the cognitive behavioral perspective

“…In particular design fluency tasks are primarily associated with the right frontal region (Ruff et al 1987), as is the left hand grip strength (Demaree et al 2002), map making, and facial affect recognition (Suberi and McKeever 1977). The right posterior region is associated with visuospatial praxis (Rao 2000), visuospatial memory (Hellige et al 1979), verbal prosody (Ross 2000), and facial recognition (Ekman and Friesen 1971). Conversely, the left hemisphere is typically associated with verbal fluency, speech production and reception (Damasio and Damasio 2000), and verbal memory (Max 2004).…”

Dual hemispheric processing in a letter matching task

“…They found further support for the notion of sustained activational asymmetries between the hemispheres. Finally, in a series of experiments examining the effect of concurrent memory loads upon visual laterality patterns, Hellige, Cox, and Litvac (1979) have concluded that the hemispheres function as information processing systems that can be influenced somewhat separately from one another and can sustain different levels of activation. On the basis of these findings, it may be suggested that in the present paradigm the appearance of stimuli on one side or the other of the visual field serves to activate the contralateral hemisphere.…”