Escape from deficits in sodium intake after thalamic lesions as a function of preoperative experience

Saline and water intakes in response to treatments with a natriuretic agent and a mineralocorticoid were studied in intact rats and in rats with lesions centered in the taste delay of the thalamus. Intact rats responded to the treatments by increasing both saline and water intake. Rats with thalamic lesions that had never drunk saline prior to induction of the lesions generally did not increase their saline intake in response to the treatments but showed normal increases in water intake. In contrast, rats with thalamic lesions that had drunk saline prior to induction of the lesions showed normal increases in both saline and water intake. Preoperative experience of sodium need did not protect rats against the lesion-induced deficit.     

The factor structure of ADHD items in DSM-III-R: Internal consistency and external validation

Previous research employing factor-analytic procedures to study the underlying dimensions of DSM-III attention deficit disorder with hyperactivity (ADDH) symptoms have consistently supported a two-factor model. Revision of the structure of the ADHD diagnosis in DSM-HI-R, as well as inclusion of new items, has raised the question of comparability of the two diagnoses. To explore the significance of these changes, teacher ratings of DSM-III ADDH items and DSM-III-R ADHD items of 85 nonreferred school children were factor-analyzed to determine their underlying factor structures. A similar two-factor solution was obtained for each diagnostic scale. The factors consisted of items believed to reflect inattention and hyperactivity-impulsivity constructs. These factors were further evaluated against results of a cognitive test battery to ascertain whether objective, external validation could be demonstrated. The hyperactivity-impulsivity factor scores were related to continuous performance test measures of response inhibition, while inattention-disorganization factor scores were related to measures of attention and visual search. Implications for assessment and diagnosis of ADHD are discussed.The authors gratefully acknowledge the assistance of Sister Hildegarde Koger, the St. Francis de Sales School, and the parents and children who participated in this study.     

On the relationship between the redundant signals effect and temporal order judgments: parametric data and a new model

Paradigms used to study the time course of the redundant signals effect (RSE; J. O. Miller, 1986) and temporal order judgments (TOJs) share many important similarities and address related questions concerning the time course of sensory processing. The author of this article proposes and tests a new aggregate diffusion-based model to quantitatively explain both the RSE and TOJs and the relationship between them. Parametric data (13 stimulus onset asynchronies) from an experiment with pairs of visual stimuli (626-nm LEDs) confirm that, relative to central signals (3 degrees), peripheral signals (35 degrees) yield slower reaction times, more strongly modulated RSE time-course functions, and flatter TOJ psychometric functions. All of these qualitative features are well captured, even in quantitative detail, by the aggregate diffusion model.     

The mind as a process

Essentially all behavior is regulated by the brain in response to information received from within the body or from the environment. The tangible structures of the brain serve as devices for processing thoughts and emotions as well as information. Stored among the interacting neural structures are memories of past experiences and responses to them. These intangibles participate in determining the decisions made and the actions performed by the brain’s structures. There are valuable studies of the clinical and neurological effects of environmental stimuli, but we need to learn more about the processes that lead to these effects. More definitive correlations could be made between environmental stimuli and the neurological pathways they create by studying individual’s real life experiences rather than laboratory simulations alone.