Cognitive Science

The degree of commonality between the perceptual mechanisms involved in processing faces and objects of expertise is intensely debated. To clarify this issue, we recorded occipito-temporal event-related potentials in response to faces when concurrently processing visual objects of expertise. In car experts fixating pictures of cars, we observed a large decrease of an evoked potential elicited by face stimuli between 130 and 200 msec, the N170. This sensory suppression was much lower when the car and face stimuli were separated by a 200-msec blank interval. With and without this delay, there was a strong correlation between the face-evoked N170 amplitude decrease and the subject's level of car expertise as measured in an independent behavioral task. Together, these results show that neural representations of faces and nonface objects in a domain of expertise compete for visual processes in the occipito-temporal cortex as early as 130–200 msec following stimulus onset.

Families of children with attention deficit hyperactivity disorder (ADHD) report more negative family relationships than families of children without ADHD. Questions remain as to the role of genetic factors underlying associations between family relationships and children's ADHD symptoms, and the role of children's ADHD symptoms as an evocative influence on the quality of relationships experienced within such families. Utilizing the attributes of two genetically sensitive research designs, the present study examined associations between biologically related and nonbiologically related maternal ADHD symptoms, parenting practices, child impulsivity/activation, and child ADHD symptoms. The combined attributes of the study designs permit assessment of associations while controlling for passive genotype-environment correlation and directly examining evocative genotype-environment correlation (rGE); two relatively under examined confounds of past research in this area. A cross-sectional adoption-at-conception design (Cardiff IVF Study; C-IVF) and a longitudinal adoption-at-birth design (Early Growth and Development Study; EGDS) were used. The C-IVF sample included 160 mothers and children (age 5-8 years). The EGDS sample included 320 linked sets of adopted children (age 6 years), adoptive-, and biologically related mothers. Questionnaires were used to assess maternal ADHD symptoms, parenting practices, child impulsivity/activation, and child ADHD symptoms. A cross-rater approach was used across measures of maternal behavior (mother reports) and child ADHD symptoms (father reports). Significant associations were revealed between rearing mother ADHD symptoms, hostile parenting behavior, and child ADHD symptoms in both samples. Because both samples consisted of genetically unrelated mothers and children, passive rGE was removed as a possible explanatory factor underlying these associations. Further, path analysis revealed evidence for evocative rGE processes in the longitudinal adoption-at-birth study (EGDS) from biologically related maternal ADHD symptoms to biologically unrelated maternal hostile parenting through early disrupted child behavior (impulsivity/activation), with maternal hostile parenting and disrupted child behavior associated with later child ADHD symptoms, controlling for concurrent adoptive mother ADHD symptoms. Results highlight the importance of genetically influenced child ADHD-related temperamental attributes on genetically unrelated maternal hostility that in turn links to later child ADHD symptoms. Implications for intervention programs focusing on early family processes and the precursors of child ADHD symptoms are discussed.

Covert shifts of attention have been shown to improve detection and discrimination thresholds for a range of visual stimuli. Although there is some evidence to suggest that the allocation of attention to a particular region of interest occurs in a retinotopic frame of reference, the importance of an allocentric, or object-based, framework has gained widespread empirical support. The current experiment investigates the nature of the spatial representation in which covert shifts of attention occur in response to a reflexive prime. Primes and targets were presented in four conditions designed to vary systematically the validity of the spatial relationship between the prime and target in egocentric or allocentric coordinate frameworks. A significant advantage, in terms of reaction time and correct identification, was found for targets located in positions previously primed in an egocentric (but not allocentric) framework whereas there was no advantage for locations primed in an allocentric (but not egocentric) framework. These results suggest that the allocation of covert spatial attention within an egocentric framework may be more important than previously thought.

Simultaneous search for one of two targets is slower and less accurate than search for a single target. Within the Signal Detection Theoretic (SDT) framework, this can be attributed to the division of resources during the comparison of visual input against independently cued targets. The current study used one or two cues to elicit single- and dual-target searches for orientation targets among similar and dissimilar distractors. In Experiment 1, the accuracy of target discrimination in brief displays was compared at setsizes of 1, 2 and 4. Results revealed a reduction in accuracy that scaled with the product of set size and the number of cued targets. In Experiment 2, the accuracy and latency of observers’ saccadic targeting were compared. Fixations on single-target searches were highly selective towards the target. On dual-target searches, the requirement to detect one of two targets produced a significant reduction in target fixations and equivalent rates of fixations to distracto...

The locations of visual objects and events in the world are represented in a number of different coordinate frameworks. For example, a visual transient is known to attract (exogenous) attention and facilitate performance within an egocentric framework. However, when attention is allocated voluntarily to a particular visual feature (ie endogenous attention), the location of that feature appears to be variously encoded either within an allocentric framework or in a spatially invariant manner. In three experiments we investigated the importance of location for the allocation of endogenous attention and whether egocentric and/or allocentric spatial frameworks are involved. Primes and targets were presented in four conditions designed to vary systematically their spatial relationships in egocentric and allocentric coordinates. A reliable effect of egocentric priming was found in all three experiments, which suggests that endogenous shifts of attention towards targets defined by a particu...

SUMMARY The cost of searching for two visual targets simultaneously was compared against two separate single-target searches using exposure time and accuracy measures within a staircase procedure. Dual-target search for all stimuli (colour, shape and orientation) exhibited a ...

Phenylketonuria is an inherited metabolic disease, which is characterized by an increased level of serum phenylalanine. Quantitative measurement of phenylalanine in the serum of phenylketonuria patients is necessary to confirm the disease, and to distinguish phenylketonuria from other forms of hyperphenylalaninemia. In this study, we report a rapid and inexpensive micro-assay for simultaneous detection and quantitative measurement of serum phenylalanine on dry blood-spots. Analysis of the standard curve showed a broad linear range for phenylalanine from 120 to 1800 micromol/L. Application of this method, the standard Guthrie bacterial inhibition assay and a high-performance liquid chromatography (HPLC) method for analysis of 34 samples from phenylketonuria patients and control samples produced comparable results, with the regression equation Y = 0.994X + 0.996. The advantage of this method over the Guthrie bacterial inhibition assay is its ability to measure serum phenylalanine quantitatively without false positive results. The method was successfully applied to dried blood-spots, serum and whole blood. The cost per sample is approximately 20-50 US cents, which is much less than for HPLC and commercial enzyme kits. The method can be automated, and is thus suitable for neonatal and mass screening for phenylketonuria, especially in developing countries where funding is a limiting factor.

Multiple sclerosis (MS) is one of the most common diseases of the central nervous system (CNS) in the Iranian population. To date, association of many genes with the prevalence and progression of the disease have been investigated. In the present study, the impact of rs1738074 single nucleotide polymorphism (SNP) in the TAGAP gene (TAGAP rs1738074) on the risk of MS was evaluated in a sample of the Iranian population. In a case control study, genotyping was performed on 300 patients and normal individuals. The data were analyzed using Pearson's chi-square test. The results showed a significant difference in the SNP frequency between case and control groups (p-value=0.049). The genotype frequencies of TT, TC and CC in patients were 10.67%, 51.33% and 38%, respectively, and in normal individuals were 20.66%, 42.67% and 36.67%, respectively. The results showed a significant difference in the genotype frequency of T/T between the patient and control groups (p<0.05). Interestingly...

The purpose of this study is to describe possible differences in cognitive functioning between smoking and non-smoking patients with first-episode psychosis and to determine whether there is a better cognitive profile associated with smoking. We assessed 61 first-episode psychosis patients with a neuropsychological battery that included computerized measurements of attention, working memory, and executive functioning. Patients were grouped into two categories: non-smokers (0 cigarettes/day; n = 30) and smokers (>/=20 cigarettes/day; n = 31). No significant differences were detected in sociodemographic and clinical data between the two groups. For attention tasks, smokers exhibited shorter reaction times in the sustained attention test than non-smokers (P = 0.039) and needed less time to complete the Stroop interference test (P = 0.013). In the working memory task, smokers exhibited shorter reaction times (P = 0.029) and presented a significantly lower percentage of omission (P = 0.002) and commission errors (P = 0.020) than non-smokers. For executive functioning, no differences were detected between groups in performance on the Wisconsin Card Sorting Test. Results indicate that first-episode psychosis patients who are nicotine users have better cognitive functioning in the areas of attention and working memory than patients who are not nicotine users. This study supports the cognitive approach to the self-medication hypothesis, to explain the high rates of cigarette smoking among psychosis patients. These results may be relevant for developing new strategies involving nicotinic receptors for cognitive enhancement in psychosis.

The self-medication hypothesis attempts to explain the extraordinary high levels of cigarette smoking in schizophrenia; patients may smoke in an attempt to reduce their cognitive deficits, symptoms, or the side effects of antipsychotics. In a previous report, we detected beneficial performance in attention and working memory in patients with first-episode psychosis who smoked compared to non-smoking patients soon after stabilization.

The main purpose was to offer evidence for the hypothesis that the stronger an acute real life stressor, namely, hearing from the physician that one has breast cancer and that one has to undergo mastectomy, the greater the induced noradrenaline (NA) depletion in the central nervous system (CNS) and the more the patient loses hope to recover. The data were derived from answers to interviews, questionnaires, and analyses of blood samples obtained from the patients on the day of admission to the hospital for a biopsy and 24 hours after the surgeon communicated the results of the biopsy to the patients. Analysis showed that a decline in 3-Methoxy 4-Hydroxy Methoxy 4-Hydroxy Phenylethylene Glycol (MHPG) concentration in blood plasma samples after being informed of the diagnosis is associated with less hope of recovery. MHPG is the main metabolite of CNS noradrenaline.