Deana B. Davalos

The Effects of Extracurricular Activity, Ethnic Identification, and Perception of School on Student Dropout Rates.

With a growing Mexican American population and an increasing dropout rate predicted for this group, research is needed to examine ways of deterring this trend and increasing retention rates. The current study examined extracurricular activity, perception of school, and ethnic identification, and the association with school retention rates among Mexican American and White non-Hispanics. Individuals reporting participation in extracurricular activity were 2.30 times more likely to be enrolled in school than were those not participating in extracurricular activity. Those Mexican Americans reporting a higher White non-Hispanics ethnic identity level were 2.41 times more likely to be enrolled in school and had a more positive perception of school than did Mexican American individuals reporting low levels of White non-Hispanics ethnic identification.

Untreated prenatal maternal depression and the potential risks to offspring: a review

Research exploring the effects of prenatal maternal depression on a developing fetus and child is underrepresented in the literature. Empirical papers have typically focused on the effects of postpartum depression (after birth) instead of prepartum depression (before birth). Disparate empirical findings have produced ongoing debate regarding the effects of prenatal depression on a developing fetus and later in infancy and early childhood. Even more controversial is determining the role of antidepressant medication on offspring outcomes and whether research that does not include the proper control population (e.g., unmedicated depressed participants) can adequately address questions about risks and benefits of treatment during pregnancy. The current review systematically summarizes the literature focusing on unmedicated prenatal depression and offspring outcome and concludes that prepartum depression is highly prevalent, is associated with negative outcomes in offspring, and remains understudied.

Increased hemodynamic response in the hippocampus, thalamus and prefrontal cortex during abnormal sensory gating in schizophrenia ☆

OBJECTIVE Deficits in sensory gating are a common feature of schizophrenia. Failure of inhibitory gating mechanisms, shown by poor suppression of evoked responses to repeated auditory stimuli, has been previously studied using EEG methods. These methods yield information about the temporal characteristics of sensory gating deficits, but do not identify brain regions involved in the process. Hence, the neuroanatomical substrates of poor sensory gating in schizophrenia remain largely unknown. This study used functional magnetic resonance imaging (fMRI) to investigate the functional neuroanatomy of sensory gating deficits in schizophrenia. METHODS Twelve patients with schizophrenia and 12 healthy comparison subjects were scanned at 3 Tesla while performing a sensory gating task developed for fMRI. P50 EEG evoked potential recordings from a paired-stimulus conditioning-test paradigm were obtained from the same subjects. RESULTS Compared to healthy comparison subjects, patients with schizophrenia exhibited greater activation in the hippocampus, thalamus, and dorsolateral prefrontal cortex (DLPFC) during the fMRI sensory gating task. No group difference was observed in the superior temporal gyrus. Schizophrenia subjects also showed decreased P50 suppression as measured with EEG. Hemodynamic response in the fMRI measure was positively correlated with test/conditioning ratios from the EEG sensory gating measure. CONCLUSIONS Poor sensory gating in schizophrenia is associated with dysfunction of an apparent network of brain regions, including the hippocampus, thalamus and DLPFC. Greater activation of these regions is consistent with evidence for diminished inhibitory function in schizophrenia.

Working memory, inhibition, and fluid intelligence as predictors of performance on Tower of Hanoi and London tasks.

The contributions of working memory, inhibition, and fluid intelligence to performance on the Tower of Hanoi (TOH) and Tower of London (TOL) were examined in 85 undergraduate participants. All three factors accounted for significant variance on the TOH, but only fluid intelligence accounted for significant variance on the TOL. When the contribution of fluid intelligence was accounted for, working memory and inhibition continued to account for significant variance on the TOH. These findings support argument that fluid intelligence contributes to executive functioning, but also show that the executive processes elicited by tasks vary according to task structure.

Effect of task difficulty on the functional anatomy of temporal processing.

Temporal processing underlies many aspects of human perception, performance and cognition. The present study used fMRI to examine the functional neuroanatomy of a temporal discrimination task and to address two questions highlighted by previous studies: (1) the effect of task difficulty on neuronal activation and (2) the involvement of the dorsolateral prefrontal cortex (DLPFC) in timing. Twenty healthy subjects were scanned while either judging whether the second in a pair of tones was shorter or longer in duration than the standard tone or simply responding to the presentation of two identical tones as a control condition. Two levels of difficulty were studied. Activation during the less difficult condition was observed only in the cerebellum and superior temporal gyrus. As difficulty increased, additional activation of the supplementary motor area, insula/operculum, DLPFC, thalamus and striatum was observed. These results suggest the cerebellum plays a critical role in timing, particularly in gross temporal discrimination. These results also suggest that recruitment of frontal and striatal regions during timing tasks is load-dependent. Additionally, robust activation of the dorsolateral prefrontal cortex under conditions of minimal working memory involvement supports the specific involvement of this region in temporal processing rather than a more general involvement in working memory.

Effects of interval duration on temporal processing in schizophrenia

INTRODUCTION Temporal processing has received scant attention in the literature pertaining to cognitive deficits in patients with schizophrenia. Previous research suggests that patients with schizophrenia exhibit temporal perception deficits on both auditory and visual stimuli. The current study investigated the effects of interval manipulation to (1) replicate the original findings with a larger sample and an increased number of trials (2) assess the degree to which both patients and controls can differentiate temporal changes in a range of experimental interstimulus intervals, and (3) explore whether different interstimulus interval durations pose different levels of difficulty for the patients with schizophrenia. METHODS Participants were asked to decide whether temporal intervals were shorter or longer than standard intervals on a computer-based auditory temporal perception task. The standard interval remained the same duration throughout the various tasks. The interstimulus interval separating the standard and experimental intervals varied in the range of 500, 1000, or 3000 ms. Data are presented for a sample of 16 patients with schizophrenia and 15 controls. RESULTS Data suggest that patients with schizophrenia exhibit deficits in differentiating interval durations across all paradigms compared to their control-group peers on a range of auditory tasks (p<.001). CONCLUSIONS These results are consistent with a general temporal deficit in schizophrenia. However, the roles of medication and localization are also addressed.

Age Differences in Stroop Interference: Contributions of General Slowing and Task-Specific Deficits

ABSTRACT This study examined the contributions of general slowing and task-specific deficits to age-related changes in Stroop interference. Nine hundred thirty-eight participants aged 20 to 89 years completed an abbreviated Stroop color-naming task and a subset of 281 participants also completed card-sorting, simple reaction time, and choice reaction time tasks. Age-related increases in incongruent color-naming latency and card-sorting perseverative errors were observed. Hierarchical regression analyses showed that the processing speed measures accounted for significant variance on both dependent measures, but that there was also a significant residual effect of age. An additional regression analysis showed that some of the variance in incongruent color-naming, after controlling for processing speed, was shared with the variance in perseverative errors. Overall, findings suggest that the age difference in Stroop interference is partially attributable to general slowing, but is also attributable to age-related changes in task-specific processes such as inhibitory control.

Neuropsychological deficits in children associated with increased familial risk for schizophrenia.

By studying neuropsychological performance in children genetically at-risk for schizophrenia, greater understanding may be obtained regarding the developmental processes of schizophrenia and associated cognitive weaknesses. A variety of cognitive deficits in genetically at-risk children have been reported. The present study was designed to examine cognitive tasks that have traditionally differentiated children genetically at-risk for schizophrenia (e.g. working memory) from normal children, while also assessing abilities that have received scant attention in this population. Aspects of emotional perception, verbal abilities, inhibition, visuo-spatial skills, and working memory were assessed in children of schizophrenic parents and normal children. Significant differences in performances were identified in at-risk children on measures of verbal skills, working memory and inhibition. Findings suggest that children genetically at-risk for developing schizophrenia exhibit neurocognitive weaknesses generally consistent with those noted in the literature. However, inhibition also appeared to be a cognitive process that significantly differentiated the groups. The possibility of a developmental expression of neurocognitive deficits is discussed.

Deficits in auditory and visual temporal perception in schizophrenia.

Introduction. Characteristics of time perception have not been well documented in patients with schizophrenia. The current study investigated time estimation to (1) test whether visual and auditory time perception varied between patients and controls, (2) assess the degree to which patients and controls can differentiate changes in experimental intervals, and (3) explore whether the temporal deficits suggest a general time perception deficit versus modality-specific differences. Methods. Participants were asked to decide whether temporal intervals were shorter or longer than standard intervals on computer-based auditory and visual temporal perception tasks. Data are presented for a sample of 10 patients with schizophrenia and 10 normal controls. Results. Data suggest that patients with schizophrenia exhibit deficits in differentiating subtle differences in intervals in the tens of milliseconds range, compared to their normal control peers on both auditory (p <.01) and visual perception tasks (p <.01). Conclusions. Preliminary data suggest that there is a general temporal processing deficit in schizophrenia. However, future research using complementary techniques may provide useful information regarding the specific types of temporal deficits that affect patients with schizophrenia and the physiology of the dysfunction.

Nicotine enhances automatic temporal processing as measured by the mismatch negativity waveform

INTRODUCTION Cholinergic agonists and, more specifically, nicotine, have been found to enhance a number of cognitive processes. The effect of nicotine on temporal processing is not known. The use of behavioral measures of temporal processing to measure its effect could be confounded by the general effects of nicotine on attention. Mismatch negativity (MMN) has been used as a physiological measure of automatic temporal processing to avoid this potential confound. METHODS A total of 20 subjects (11 nonsmokers and 9 smokers following 2 hr of abstinence) participated in a two-visit single-blind, placebo-controlled crossover study of the effect of nicotine on MMN indices in response to an interstimulus interval deviant. RESULTS Nicotine-enhanced MMN amplitudes from baseline recording to postdrug recording greater than did the placebo condition. This enhancement was seen in both nonsmokers and smokers. Nicotine had no significant effect on MMN latency or N100 amplitude or latency. DISCUSSION This is the first study to demonstrate a nicotine-related enhancement of MMN amplitude to an interstimulus interval duration deviant and confirms our hypothesis that nicotine enhances preattentive temporal processing. Nicotinic agonists may represent a potential therapeutic option for individuals with abnormalities in early sensory or temporal processing related to cholinergic system abnormalities. Methodologically, our paradigm of nicotine administration in abstinent smokers is important because it resulted in both minimal withdrawal symptoms and meaningful data that are not attributable solely to relief of withdrawal.