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Gamma band modulations in neural activity have been proposed to mediate attentional processes. To support a causal link between gamma activity and attentional selection, we attempt to evoke gamma oscillations by a 50-Hz subliminal flicker. We find that a subliminal 50-Hz flicker at a target location, before target presentation, speeds up and enhances target detection and discrimination. This effect is specific to the middle of the gamma range because it is not evident at visual attention | neural synchrony | gamma | psychophysics | subliminal

Children with unilateral pre-or perinatal brain injury (BI) show remarkable plasticity for language learning. Previous work highlights the important role that lesion characteristics play in explaining individual variation in plasticity in the language development of children with BI. The current study examines whether the linguistic input that children with BI receive from their caregivers also contributes to this early plasticity, and whether linguistic input plays a similar role in children with BI as it does in typically developing (TD) children. Growth in vocabulary and syntactic production is modeled for 80 children (53 TD, 27 BI) between 14 and 46 months. Findings indicate that caregiver input is an equally potent predictor of vocabulary growth in children with BI and in TD children. In contrast, input is a more potent predictor of syntactic growth for children with BI than for TD children. Controlling for input, lesion characteristics (lesion size, type, seizure history) also affect the language trajectories of children with BI. Thus, findings illustrate how both variability in the environment (linguistic input) and variability in the organism (lesion characteristics) work together to contribute to plasticity in language learning. Keywords: linguistic input, language development, early brain injury, functional plasticity, lesion characteristics

This special section of Developmental Psychology contains articles on the interplay of biology and the environment, broadly defined, that have the potential to change or challenge how developmental psychologists think. Topics include how experience affects gene expression; how genes affect how the environment is experienced and what effect the environment has; interactions between the environment and the presence or absence of early brain damage; motor neurons and the understanding of others' beliefs and intentions; the effect of physical fitness on cognition and the brain; evidence that our brains work and develop differently from the way traditionally thought; misconceptions that can arise from treating children as if they are simply small adults; and how research with adults can provide insights into developmental processes in children. Each of the 16 articles in the special section forges new territory and crosses disciplinary boundaries. They suggest that investigators look at variables not typically considered, or look at them from perspectives not usually taken, and especially that they pay more attention to interrelations among variables. Keywords: epigenesis, brain development, physical exercise, neuronal synchronous oscillations, Gene x Environment interactions

Some species and individuals are able to learn cognitive skills more flexibly than others. Learning experiences and cortical function are known to contribute to such differences, but the specific factors that determine an organism's intellectual capacities remain unclear. Here, an integrative framework is presented suggesting that variability in cognitive plasticity reflects neural constraints on the precision and extent of an organism's stimulus representations. Specifically, it is hypothesized that cognitive plasticity depends on the number and diversity of cortical modules that an organism has available as well as the brain's capacity to flexibly reconfigure and customize networks of these modules. The author relates this framework to past proposals on the neural mechanisms of intelligence, including (a) the relationship between brain size and intellectual capacity; (b) the role of prefrontal cortex in cognitive control and the maintenance of stimulus representations; and (c) the impact of neural plasticity and efficiency on the acquisition and performance of cognitive skills. The proposed framework provides a unified account of variability in cognitive plasticity as a function of species, age, and individual, and it makes specific predictions about how manipulations of cortical structure and function will impact intellectual capacity. Keywords: cognitive neuroscience, comparative cognition, evolution, cortical column, neuromodulation

There is controversy over the nature of the disturbance in brain development that underpins attention-deficit/hyperactivity disorder (ADHD). in particular, it is unclear whether the disorder results from a delay in brain maturation or whether it represents a complete deviation from the template of typical development. Using computational neuroanatomic techniques, we estimated cortical thickness at >40,000 cerebral points from 824 magnetic resonance scans acquired prospectively on 223 children with ADHD and 223 typically developing controls. With this sample size, we could define the growth trajectory of each cortical point, delineating a phase of childhood increase followed by adolescent decrease in cortical thickness (a quadratic growth model). From these trajectories, the age of attaining peak cortical thickness was derived and used as an index of cortical maturation. We found maturation to progress in a similar manner regionally in both children with and without ADHD, with primary sensory areas attaining peak cortical thickness before polymodal, high-order association areas. However, there was a marked delay in ADHD in attaining peak thickness throughout most of the cerebrum: the median age by which 50% of the cortical points attained peak thickness for this group was 10.5 years (SE 0.01), which was significantly later than the median age of 7.5 years (SE 0.02) for typically developing controls (log rank test [chi][(1).sup.2] = 5,609, P < 1.0 x [10.sup.-20]). The delay was most prominent in prefrontal regions important for control of cognitive processes including attention and motor planning. Neuroanatomic documentation of a delay in regional cortical maturation in ADHD has not been previously reported. cortical development | structural neuroimaging

Cognitive memory involves long-term memories for facts (semantic memory) and personal experiences (episodic memory) that can be brought to mind. There is consensus that the hippocampus and related medial temporal lobe (MTL) structures are crucial for adult cognitive memory, but much less is known about their contribution to memory during infancy and childhood. We argue that the MTL is involved in memory from early in life, supporting recognition memory within the first postnatal months and recall memory within the first year. We propose that normal development involves a sequence in which a form of semantic-like memory emerges first, whereas the characteristics of episodic memory develop only later with progressive development of the hippocampus. Early bilateral injury to the hippocampus disrupts this normal pattern such that memory skills cannot develop beyond the stage of semantic memories. This review is part of the INMED/ TINS special issue Nature and nurture in brain development and neurological disorders, based on presentations at the annual INMED/TINS symposium (http://inmednet.com/).

Assembly of neuronal circuits is controlled by the sequential acquisition of neuronal subpopulation-specific identities at progressive developmental steps. Whereas neuronal features involved in initial phases of differentiation are already established at cell-cycle exit, recent findings, based mainly on work in the peripheral nervous system, suggest that the timely integration of signals encountered en route to targets and from the target region itself is essential to control late steps in connectivity. As neurons project towards their targets they require target-derived signals to establish mature axonal projections and acquire neuronal traits such as the expression of distinct combinations of neurotransmitters. Recent evidence presented in this review shows that this principle, of a signaling interplay between target-derived signals and neuronal cell bodies, is often mediated through transcriptional events and is evolutionarily conserved.

Paul Churchland's 'The Engine of Reason, the Seat of the Soul' seeks to prove that greater understanding of the brain will improve the chances of helping those whose brains do not function as they should. Churchland likes the idea that minds are essentially interacting assemblies of recurrent neural networks. There are biochemical processes in the brain as well as electrical-synaptic transmission, a problem with seeing the mind as assembled recurrent networks.

Can dysfunction in neural systems subserving emotion lead, under certain circumstances, to more advantageous decisions? To answer this question, we investigated how normal participants, patients with stable focal lesions in brain regions related to emotion (target patients), and patients with stable focal lesions in brain regions unrelated to emotion (control patients) made 20 rounds of investment decisions. Target patients made more advantageous decisions and ultimately earned more money from their investments than the normal participants and control patients. When normal participants and control patients either won or lost money on an investment round, they adopted a conservative strategy and became more reluctant to invest on the subsequent round; these results suggest that they were more affected than target patients by the outcomes of decisions made in the previous rounds.

Rips et al. appear to discuss, and then dismiss with counterexamples, the brain-based theory of mathematical cognition given in Lakoff and Nunez (2000). Instead, they present another theory of their own that they correctly dismiss. Our theory is based on neural learning. Rips et al. misrepresent our theory as being directly about real-world experience and mappings directly from that experience.

The impact of a brain injury on the psychological and neurological behavior of a person is explained. The several conditions which actually affect this behavior are listed.