Effects of prefrontal and parietal neuromodulation on magnitude processing and integration.

Numerical cognition is an essential skill for survival, which includes the processing of discrete and continuous quantities, involving a mainly right fronto-parietal network. However, the neurocognitive systems underlying the processing and integration of discrete and continuous quantities are currently under debate. Noninvasive brain stimulation techniques have been used in the study of the neural basis of numerical cognition with a spatial, temporal and functional resolution superior to other neuroimaging techniques. The present randomized sham-controlled single-blinded trial addresses the involvement of the right dorsolateral prefrontal cortex and the right intraparietal sulcus in magnitude processing and integration. Multifocal anodal transcranial direct current stimulation was applied online during the execution of magnitude comparison tasks in three conditions: right prefrontal, right parietal and sham stimulation. The results show that prefrontal stimulation produced a moderated decrease in response times in all magnitude processing and integration tasks compared to sham condition. While parietal stimulation had no significant effect on any of the tasks. The effect found is interpreted as a generalized improvement in processing speed and magnitude integration due to right prefrontal neuromodulation, which may be attributable to domain-general or domain-specific factors.

Trastorno del espectro alcohólico fetal: Un trastorno del neurodesarrollo infradiagnosticado y de pronóstico incierto / Fetal alcohol spectrum disorder. An underdiagnosed neuro-development disorder of uncertain prognosis

La exposición prenatal al alcohol es causa de alteraciones somáticas, cognitivas y conductuales que se agrupan bajo el término de trastorno del espectro alcohólico fetal (TEAF). La evolución a largo plazo de los sujetos afectados a menudo es desfavorable, especialmente a nivel académico y adaptativo social. En el perfil neuropsicológico es característica la disfunción ejecutiva a menudo asociada a trastornos de la conducta que evolucionan en muchos casos hacia la delincuencia a partir de la adolescencia y en la edad adulta. Se han descrito también déficits de las habilidades sociales y la empatía. La exposición prenatal al alcohol constituye la causa más frecuente de trastorno del neurodesarrollo adquirido y prevenible.

Prenatal exposure to alcohol is the cause of cognitive and behavioural disorders grouped under the term fetal alcohol spectrum disorders (FASD). The long-term evolution of subjects with FASD is often unfavourable, especially in social and academic fields. Executive dysfunction is a hallmark deficit for children with FASD with increased rates of externalizing behaviours, such as aggressiveness and frequently delinquency in adolescence and adulthood. Deficits in social skills, empathy and communication ability are frequent observed among FASD. Prenatal exposure to alcohol is the most frequent cause of acquired and preventable neurodevelopmental disorder.

Neuropsychological functioning and age-related changes in schizophrenia and/or cocaine dependence.

Although little is known about the combined effects of Schizophrenia (SZ) and Substance Use Dependence (SUD) in neurocognitive functioning, the current literature points out that performance depends on the specific cognitive domains, the age of individuals and the type of substance of abuse. Our aim is to elucidate, in a sample with SZ and/or cocaine dependent individuals in remission for more than 4 months, their performance in attention, verbal memory and speed of processing, taking into account the possible effect of both age and duration of SUD. The total sample consisted of 95 male patients, aged 20 to 60 years, divided in three groups: one group with SZ and cocaine dependence (SZ+), another group with SZ without cocaine dependence (SZ-) and a third group with cocaine dependence without psychiatric comorbidity (COC). Our results show that those SZ+ who were abstinent for more than four months did not differ from their SZ- counterparts in the neuropsychological functioning. Both SZ groups performed significantly worse than the COC group. A negative impact of age on the neuropsychological performance was found in the SZ+ group, suggesting additive later cognitive deficits in SZ+ patients due to the long-term brain damage of SUD.

Executive functioning in individuals with schizophrenia and/or cocaine dependence.

OBJECTIVE: Although little is known about neurocognition in Dual Diagnosis, it has been suggested that Schizophrenia (SZ) patients with comorbid substance use belong to a subgroup with lower genetic vulnerability to develop SZ and, consequently, they show better executive and social premorbid functioning. The first aim of this study was to assess the executive functioning, and the second one was to explore the effect of age of onset of substance use in neurocognition in SZ patients with cocaine dependence. METHODS: The total sample consisted of 95 male patients, aged 20 to 60 years, divided in three groups: one group with SZ and cocaine dependence (SZ+; n = 30), another group with SZ without cocaine dependence (SZ-; n = 30), and a control group with cocaine dependence without psychiatric comorbidity (COC; n = 35). RESULTS: We found a better executive functioning in both SZ+ and COC than SZ-. We observed a worse performance of SZ+ patients compared with COC in cognitive set-shifting regardless the age of onset of consumption. CONCLUSIONS: The results agree with the hypothesis of a lower genetic vulnerability in SZ+ patients to develop psychosis compared with SZ-, who develop it without any additional trigger. However, future research is needed to clarify the current knowledge gaps.

Effects of caffeine and glucose, alone and combined, on cognitive performance.

OBJECTIVE: To study the effects of consuming caffeine and glucose, alone and combined, on cognitive performance. METHODS: Seventy-two healthy subjects (36 women; age range 18-25) were tested early in the morning, having fasted overnight. Using a double-blind, randomised design, subjects received one of the following beverages: water (150 ml); water plus 75 mg of caffeine; water plus 75 g of glucose; water plus and 75 mg of caffeine and 75 g of glucose. Attention, manual dexterity, visuo-spatial and frontal functions, memory (immediate, consolidation and working) and subjective state were all assessed. RESULTS: The combination of caffeine and glucose had beneficial effects on attention (sequential reaction time tasks) and on learning and consolidation of verbal memory, effects not being observed when either substance was administered alone. Caffeine only showed improvement in simple reaction time and glucose in simple and one sequential reaction time tasks and in the manual dexterity assembly task. CONCLUSIONS: The results indicate that the synergistic effects of caffeine and glucose can benefit sustained attention and verbal memory, even with adequate levels of activation of the subjects. However, further studies are required, controlling for different levels of cognitive effort and also considering measurements of neural activity.

Impact of the COMT Val108/158 Met and DAT genotypes on prefrontal function in healthy subjects.

Two limiting factors of dopamine activity are the catechol-o-methyltransferase (COMT) and the dopamine transporter (DAT), which terminate dopamine activity by degradation and uptake, respectively. Genetic variants of COMT and DAT have been related to the enzymatic activity and protein availability, respectively. The Met allele of the COMT Val108/158 Met polymorphism has been associated to lower enzymatic activity and the 9-repeat allele of the DAT 40 base-pair (bp) variable number of tandem repeat (VNTR) polymorphism has been related to lower protein availability. Genotypes for COMT and DAT were determined in a sample of 75 healthy subjects, who underwent functional magnetic resonance imaging (fMRI) while performing an N-back task. To further assess the effects of the genotypes on cognition, subjects were administered the Wisconsin Card Sorting Test (WCST) and the Continuous Performance Test (CPT). Analysis of fMRI data revealed an additive effect of these two genes on brain activation in an N-back task, with subjects homozygous for the Val and the 9-repeat alleles showing the highest activation for the same level of performance. Moreover, the Val allele was related to higher number of perseverative errors on the WCST and with a higher number of commission errors on the CPT. The 10-repeat allele was associated with faster reaction times but also with a higher number of commission errors. Our results support a role of the COMT Val108/158 Met and the DAT 40 bp VNTR in both brain activation and cognition.

Secuelas neuropsicológicas de los traumatismos craneoencefálicos / Neuropsychological sequelae of traumatic brain injury

Hoy en día, el neuropsicólogo clínico se encuentra con numerosos pacientes que sobreviven al traumatismo craneoencefálico (TCE) con importantes secuelas neurológicas debido, en parte, a la mejora de las técnicas terapéuticas. Las alteraciones neuropsicológicas en los TCE están directamente relacionadas con los mecanismos fisiopatológicos subyacentes y con variables biológicas y demográficas. La valoración de los efectos del TCE, necesita de la comprensión de la fisiopatología y de la realización de estudios de neuroimagen, que aportan datos estructurales y funcionales relevantes. El patrón característico de daño cerebral que presentan los TCE moderados y graves es de daño no específico y generalizado, pero con gran afectación de los lóbulos frontal y temporal. El tipo de afectación cerebral se refleja en las funciones que se encuentran alteradas tras un TCE, que en la mayoría de los casos, son la atención, la memoria, las funciones frontales, la emoción y la conducta (AU)

Amygdalar atrophy in panic disorder patients detected by volumetric magnetic resonance imaging.

It has been suggested that the pathophysiology of panic disorder (PD) may involve abnormalities in several brain structures, including the amygdala. To date, however, no study has used quantitative structural neuroimaging techniques to examine amygdalar anatomy in this disorder. Volumetric magnetic resonance imaging (MRI) studies of the amygdalas, hippocampi, and temporal lobes were conducted in 12 drug-free, symptomatic PD patients (six females and six males), and 12 case-matched healthy comparison subjects. Volumetric MRI data were normalized for brain size. PD patients were found to have smaller left-sided and right-sided amygdalar volumes than controls. No differences were found in either hippocampi or temporal lobes. These findings provide new evidence of changes in amygdalar structure in PD and warrant further anatomical and MRI brain studies of patients with this disorder.

Parahippocampal gray matter density in panic disorder: a voxel-based morphometric study.

OBJECTIVE: The authors examined possible cerebral gray matter abnormalities in patients with panic disorder. METHOD: Gray matter concentration in 18 panic disorder outpatients and 18 healthy subjects was compared by using a voxel-based morphometry approach. RESULTS: Gray matter density of the left parahippocampal gyrus was significantly lower in patients with panic disorder compared with healthy subjects. CONCLUSIONS: This result provides further support for the involvement of the parahippocampal area in the pathophysiology of panic disorder.