The effect of thalamic stimulation in processing of verbal stimuli in dichotic listening tasks: a case study

In dichotic listening tasks, the (dominant) right ear's superiority in processing verbal stimuli has been attributed to its direct anatomic connection with the left dominant hemisphere. The role played by extralinguistic factors, such as attention and functional tuning of the associated cortical structures, has not been carefully examined. This investigation was undertaken to evaluate the effects of the left thalamic electric stimulation on the processing (recognition and recall) of dichotically presented CVC verbal stimuli in a patient being treated for chronic pain. We report the positive effects of electric stimulation (confirmed by increased subcortical metabolic activity using SPECT, a brain imaging technique) on the processing of dichotically presented verbal stimuli.     

Performance as a function of resultant achievement motivation (perceived ability) and perceived difficulty

Subjects worked on a task which was described as either easy or difficult. When the task was thought to be difficult, Ss high in resultant achievement motivation performed better than those low in resultant achievement motivation. However, when the task was perceived as easy, the high motive group performed worse than the low group. These results confirm a prediction from Kukla's attributional theory of performance, in which resultant achievement motivation is conceived as a measure of perceived ability. They are not, however, deriveable from Spence's theory of the effects on performance of objective task difficulty, nor from Weiner's hypothesis concerning the motivational effects of success and failure. On the other hand, Kukla's theory provides an explanation for both the data usually cited in support of Spence's position and those taken to confirm Weiner's hypothesis. The relationship between the present results and Atkinson's theory of achievement motivation, which also hypothesizes an effect of perceived difficulty on performance, is discussed.     

Metacognition in argument generation: the misperceived relationship between emotional investment and argument quality

Overestimation of one’s ability to argue their position on socio-political issues may partially underlie the current climate of political extremism in the U.S. Yet very little is known about what factors influence overestimation in argumentation of socio-political issues. Across three experiments, emotional investment substantially increased participants’ overestimation. Potential confounding factors like topic complexity and familiarity were ruled out as alternative explanations (Experiments 1–3). Belief-based cues were established as a mechanism underlying the relationship between emotional investment and overestimation in a measurement-of-mediation (Experiment 2) and manipulation-of-mediator (Experiment 3) design. Representing a new bias blind spot, participants believed emotional investment helps them argue better than it helps others (Experiments 2 and 3); where in reality emotional investment harmed or had no effect on argument quality. These studies highlight misguided beliefs about emotional investment as a factor underlying metacognitive miscalibration in the context of socio-political issues.     

Dissociating the effects of attention and contingency awareness on evaluative conditioning effects in the visual paradigm

Two experiments are described that investigate the effects of attention in moderating evaluative conditioning (EC) effects in a picture-picture paradigm in which previously discovered experimental artifacts (e.g., Field & Davey, 1999 ) were overcome by counterbalancing conditioned stimuli (CSs) and unconditioned stimuli (USs) across participants. Conditioned responses for individuals who had attention enhanced were compared against a control group and groups for whom attention was impeded using a distracter task. In a second experiment the effects of attention were dissociated from those of contingency awareness by using backward-masked US presentations. The results of these experiments indicate that although associative EC effects may not be disrupted by a lack of contingency awareness, attention is an important factor in establishing conditioning. These results shed some light onto the possible boundary conditions that could explain past inconsistencies in obtaining EC effects in the visual paradigm.     

Right-hemispheric language evidence from cortical stimulation

While the left-hemispheric dominance for language in most right-handers is unquestionable, clinical observations suggest that the right, nondominant hemisphere has a considerable capacity for language. Under certain neuroanatomical conditions, the right-hemispheric capacity becomes functional and, thus, measurable. This study focuses on evoked language responses during electrical stimulation of the right hemisphere in three left-dominant patients undergoing temporal lobe resections for medically intractable seizures.     

The hippocampus and stress induced 17-OHCS elevations

The physiologic contribution of the limbic brain to emotionally induced stress is still poorly understood. The present study is designed to more specifically evaluate the role of the hippocampus in stress induced plasma 17-OHCS elevations. The conditional reflex to a sequential presentation of tone and shock was used as the stress agent in adult mongrel dogs. Plasma 17-OHCS levels were determined by the Porter-Silber method. Control and stress levels of 17-OHCS were determined before and after unilateral (left) hippocampectomy, and subsequent contralateral (right) hippocampectomy. A unilateral posterior hippocampal lesion partially attenuated (20%) the normal 17-OHCS stress response. In contrast to unilateral lesions, equivalent bilateral posterior hippocampal lesions abolished the normal 17-OHCS stress response. These observations support the thesis that the elevated 17-OHCS levels in response to the conditioning paradigm is dependent on the hippocampus. Furthermore, it is dependent upon the continuity of the hippocampal circuit and not upon the volumetric steroid binding capacity of the hippocampus. These studies also suggest that a unilaterally functioning hippocampus may be adequate to meet the physiologic needs of stress, as reflected by the 17-OHCS response. Presented at the 1978 meeting of the Pavlovian Society, St. Petersburg, Florida.