Acquisition and extinction of signaled avoidance as a function of intermittent reinforcement

Signaled, shuttle-box avoidance responding in female rats of the Fischer₃₄₄ strain was examined as a function of four separate contingencies of intermittent reinforcement. In Experiment 1, when avoidance responses during acquisition were reinforced 25% of the time with prompt CS termination, animals responded equally often during acquisition and significantly more often during extinction than animals who received such reinforcement on a 100% schedule. Similar results were found under a trace procedure in Experiment 2 when avoidance responses were reinforced 25% of the time with informational feedback stimuli. In contrast, during Experiment 3, when animals were shocked on only 25% of the trials on which they failed to respond, the level of avoidance responding during both acquisition and extinction was significantly less than it was when animals were shocked on a 100% schedule. Comparable results were found in Experiment 4 when avoidance responses during acquisition averted shock on only 25% of the trials. Thus, intermittent reinforcement contingencies involving response-contingent feedback stimuli and shock have differential effects on avoidance responding during both acquisition and extinction trials under the signaled avoidance procedure.     

Percentage body weight and the successive negative contrast effect in rats

In two runway experiments employing rats the successive negative contrast effect was evaluated for animals maintained at high or low body weights. In both experiments the effects on performance of shifting reward magnitude were independent of body weight. These results contrast with those of previous studies in which the successive negative contrast effect occurred only under low body weight. It was suggested that when conditions are maximal or near maximal for production of the successive negative contrast effect, as they were here but not in previous investigations, body weight will not influence the size of this effect.     

Brain stem electrical responses of stutterers and normals by sex,ears, and recovery

Auditory brainstem electrical responses (BSER) of right and left ears of active stutterers, recovered stutterers, and nonstutterers, both male and female adults, were obtained at click rates of 11.1 and 71.1/sec. Latency intervals of waves I, III, and V were measured. The auditory systems of subjects were stressed using a rapid rate of 71.1 clicks/sec. The latency of wave V was used as the measure of the stress condition.Analysis of variance was used to determine statistical significances of main effects and interactions of mean BSER (waves I, III, V, and wave V in stress condition) of left and right ears of male stutterers (active and recovered), female stutterers (active and recovered), and male and female nonstutterers.With one exception, all main effects and all higher order interactions were nonsignificant. The one main effect that was significant was gender. Females have significantly faster rates of neural transmission than do males. The question was raised, does this finding contribute toward an explanation of the sex ratio in stuttering?     

An evaluation of the effects of supplemental “fluency” training during maintenance

The voice onset time (VOT) of two groups of treated stutterers and a normal-speaking group was assessed by spectrographic analysis. Both groups of stutterers had significantly slower VOT than the normal speakers. The experimental group of stutterers was given 8 wk of “fluency” training designed to remediate characteristics of speech identified as related to “tenuous” fluency. The control group of stutterers received ongoing maintenance therapy. Posttreatment VOT was assessed. The experimental stuttering group had significantly decreased their VOT in the direction of the normal-speaking group, whereas the control group of stutterers had a greater VOT between pre- and posttreatment. The implication of these results for the maintenance of fluency are discussed.     

A case of literal alexia: evidence for a disconnection syndrome

We describe a patient with literal alexia, agraphia, and only minimal aphasia, resulting from a left occipito-parietal ischemic infarction. Neither impaired visual processing nor impaired oral output could explain the patient's letter reading deficit, since he retained the ability to match letters of mixed case, and remained able to spell aloud and to pronounce and comprehend orally spelled words. His residual word reading was characterized by better performance for nouns and highly imageable words than for functors , poorly imageable words, and nonwords. We propose that this patient's letter reading deficit was due to a partial disconnection of his visual from his linguistic systems, with residual word reading accomplished by a semantically mediated compensatory mechanism. We suggest, further, that the dissociations between word and letter reading observed in some alexic individuals may be attributed, in part, to a difference in the relative contributions of dorsal and ventral occipital structures to the reading process.     

Left hemisphere sensitivity to consonant sounds not displayed by the right hemisphere: electrophysiological correlates

Auditory evoked responses (AER) to a series of consonant-vowel syllables were recorded from frontal, temporal, and parietal scalp locations from 14 right-handed college students. Averaged AERs were submitted to principal components analysis and analysis of variance. Six components of the group's AERs were found to reflect various aspects of the stimulus parameters. One component reflected changes over only the left hemisphere to different consonants. A second component changed systematically over both hemispheres but did not discriminate between all consonants.     

The effect of response choice relatedness on pantomime and verbal recognition ability in aphasic patients

Twenty aphasic and twenty control subjects were examined on two versions of a pantomime recognition and a verbal recognition test; one version containing response choices conceptually/semantically related to target responses, the other containing unrelated response choices. The aphasic group was inferior to controls on the pantomime and verbal recognition tests, although the magnitude and consistency of the differences between aphasics and controls were greater for the pantomime test. The presence of conceptually/semantically related response choices on the pantomime recognition test significantly reduced test scores of aphasic patients, and this reduction was related to the magnitude of the effect of response choice relatedness on their verbal recognition test performance. The findings are consistent with an interpretation of aphasia as an impairment of a central symbolic ability which can affect processing for meaning in both verbal and nonverbal modes of communication.     

Incomplete Kluver-Bucy syndrome and fluent aphasia

A case of probable herpetic viral encephalitis is presented. The clinical picture following the acute phase of disease was dominated by severe fluent aphasia, prominent oral tendencies, visual agnosia, and a decrease in fear reactions. Most of these symptoms, with the obvious exception of aphasia, are similar to those observed by Kluver and Bucy in rhesus monkeys that underwent bitemporal lobectomy. These manifestations may be explained by the tendency of the herpes simplex virus to invade the temporal lobes. "Agnosia" in the auditory field and changes in vocal behavior were observed by H. Kluver and P. C. Bucy (1939, Archives of Neurology and Psychiatry, 42, 949-1000) in some of their bitemporal monkeys. The association of sensory aphasia, as observed in this case, with the auditory "agnosia" observed in some bitemporal monkeys, is discussed.