On solving 3CNF-satisfiability with an in vivo algorithm.

Several in vitro DNA algorithms have been proposed in the literature for solving various combinatorial search problems. The next logical step is the critical examination of whether or not such computation can be performed within the cellular environment. We consider the possibility of solving 3-conjunctive-normal-form Satisfiability with one possible in vivo algorithm. The exact biological details still remain to be defined and seem beyond the capabilities of current technologies, but perhaps, this will serve as a springboard for further theoretical inquiry into in vivo approaches.

Recognition of CVC Syllables from LVF, RVF, and Central Locations: Hemispheric Differences and Interhemispheric Interaction.

Abstract In each of two experiments, subjects were required to identify consonant-vowel-consonant nonsense syllables projected to the left visual fiel/right hemisphere (LVF/RH), right visual field/left hemisphere (RVF/LH), or to the CENTER of the visual field. There were fewer errors on RVF/LH than on LVF/RH trials and the pattern of errors was qualitatively different on RVF/LH and LVF/RH trials. The pattern of errors was consistent with the hypothesis that attention is distributed across the three letters in a relatively slow serial fashion on LVF/RH trials whereas attention is distributed more rapidly and evenly across the three letters on RVF/LH trials. Despite the large RVF/LH advantage, the qualitative pattern of errors on CENTER trials (when viewing conditions do not favor one hemisphere or the other) was very similar to the pattern obtained on LW/RH trials. Implications of this counterintuitive finding are considered for the nature of interhemispheric interaction.

Individual variation in hemispheric asymmetry: multitask study of effects related to handedness and sex.

Functional hemispheric asymmetries were examined for right- or left-handed men and women. Tasks involved (a) auditory processing of verbal material, (b) processing of emotions shown on faces, (c) processing of visual categorical and coordinate spatial relations, and (d) visual processing of verbal material. Similar performance asymmetries were found for the right-handed and left-handed groups, but the average asymmetries tended to be smaller for the left-handed group. For the most part, measures of performance asymmetry obtained from the different tasks did not correlate with each other, suggesting that individual subjects cannot be simply characterized as strongly or weakly lateralized. However, ear differences obtained in Task 1 did correlate significantly with certain visual field differences obtained in Task 4, suggesting that both tasks are sensitive to hemispheric asymmetry in similar phonetic or language-related processes.

Hemispheric asymmetry for processing unpronounceable and pronounceable letter trigrams.

In each of two experiments, observers attempted to identify three-letter strings presented briefly to the left visual field/right hemisphere (LVF/RH), to the right visual field/left hemisphere (RVF/LH), or to both visual fields (and hemispheres) simultaneously (redundant BILATERAL trials). Similar visual half-field effects were obtained for both all-consonant (CCC) strings and consonant-vowel-consonant (CVC) nonwords. For both types of strings, there were fewer errors on RVF/LH trials than on LVF/RH trials and the pattern of error types was qualitatively different for the two visual fields. The similarity of visual half-field results for CCC and CVC strings indicates that results that have been reported in earlier studies with CVC strings are not restricted to letter strings that can be coded as a single pronounceable syllable, as some have suggested. Instead, the results are consistent with hypotheses about hemispheric differences in the ability to encode and remember individual letters in a multielement display. In addition, for both CCC and CVC letter strings there were fewer errors on redundant BILATERAL trials than on either type of unilateral trial, suggesting interhemispheric collaboration in both cases. However, the qualitative error patterns obtained on redundant BILATERAL trials suggest that the precise way in which the hemispheres collaborate differs with the type of letter string.

Interhemispheric interaction when both hemispheres have access to the same stimulus information.

Right-handed Ss identified consonant-vowel-consonant (CVC) nonsense syllables presented tachistoscopically. The CVC on each trial was presented to the left visual field-right hemisphere (LVF-RH), to the right visual field-left hemisphere (RVF-LH), or the same CVC was presented to both visual fields (bilateral presentation). When recognition was incorrect, the pattern of errors was qualitatively different on LVF-RH and RVF-LH trials, suggesting that each cerebral hemisphere has its own preferred mode of processing the CVC stimuli. The qualitative pattern of errors on bilateral trials was identical to that obtained on LVF-RH trials. The bilateral results are described well by a model that assumes the mode of processing characteristic of the RH dominates on bilateral trials but is applied to both the LVF-RH and RVF-LH stimuli.