How chunks, long-term working memory and templates offer a cognitive explanation for neuroimaging data on expertise acquisition: a two-stage framework

Our review of research on PET and fMRI neuroimaging of experts and expertise acquisition reveals two apparently discordant patterns in working-memory-related tasks. When experts are involved, studies show activations in brain regions typically activated during long-term memory tasks that are not observed with novices, a result that is compatible with functional brain reorganization. By contrast, when involving novices and training programs, studies show a decrease in brain regions typically activated during working memory tasks, with no functional reorganization. We suggest that the latter result is a consequence of practice periods that do not allow important structures to be completely acquired: knowledge structures (i.e., Ericsson and Kintsch's retrieval structures; Gobet and Simon's templates) and in a lesser way, chunks. These structures allow individuals to improve performance on working-memory tasks, by enabling them to use part of long-term memory as working memory, causing a cerebral functional reorganization. Our hypothesis is that the two brain activation patterns observed in the literature are not discordant, but involve the same process of expertise acquisition in two stages: from decreased activation to brain functional reorganization. The dynamic of these two physiological stages depend on the two above-mentioned psychological constructs: chunks and knowledge structures.     

Sleep EEG changes during adolescence: An index of a fundamental brain reorganization

Delta (1–4 Hz) EEG power in non-rapid eye movement (NREM) sleep declines massively during adolescence. This observation stimulated the hypothesis that during adolescence the human brain undergoes an extensive reorganization driven by synaptic elimination. The parallel declines in synaptic density, delta wave amplitude and cortical metabolic rate during adolescence further support this model. These late brain changes probably represent the final ontogenetic manifestation of nature’s strategy for constructing nervous systems: an initial overproduction of neural elements followed by elimination. Errors in adolescent brain reorganization may cause mental illness; this could explain the typical age of onset of schizophrenia. Longitudinal studies of sleep EEG are enhancing our knowledge of adolescent brain maturation. Our longitudinal study of sleep EEG changes in adolescence showed that delta power, which may reflect frontal cortex maturation, begins its decline between ages 11 and 12 years and falls by 65% by age 17 years. In contrast, NREM theta power begins its decline much earlier. Delta and theta EEG frequencies are important to sleep theory because they behave homeostatically. Surprisingly, these brain changes are unrelated to pubertal maturation but are strongly linked to age. In addition to these (and other) maturational EEG changes, sleep schedules in adolescence change in response to a complex interaction of circadian, social and other influences. Our data demonstrate that the daytime sleepiness that emerges in adolescence is related to the decline in NREM delta as well as to altered sleep schedules. These longitudinal sleep data provide guideposts for studying cognitive and behavioral correlates of adolescent brain reorganization.     

The effects of aging on visual memory: evidence for functional reorganization of cortical networks

Recent evidence suggests that the mature human brain is capable of substantial functional reorganization following injury. The fact that the brain retains a great deal of plasticity raises the possibility that cortical reorganization may occur during normal aging. We examined this issue by using positron emission tomography (PET) to measure the brain activity associated with short-term memory for simple visual attributes in young and old observers. A two-interval forced choice procedure was used to measure spatial frequency discrimination thresholds for sine wave gratings presented at different inter-stimulus intervals (ISI). Memory load was manipulated by varying the duration of the ISI and by presenting an irrelevant masking stimulus in the middle of the ISI. Old and young observers performed the experiment equally well. However, the neural systems correlated with good performance differed for the two age groups. The results support the hypothesis that the functional networks that underlie visual memory undergo reorganization during aging.     

Multimodal interactions in typically and atypically developing children: natural versus artificial environments

This review addresses the central role played by multimodal interactions in neurocognitive development. We first analyzed our studies of multimodal verbal and nonverbal cognition and emotional interactions within neuronal, that is, natural environments in typically developing children. We then tried to relate them to the topic of creating artificial environments using mobile toy robots to neurorehabilitate severely autistic children. By doing so, both neural/natural and artificial environments are considered as the basis of neuronal organization and reorganization. The common thread underlying the thinking behind this approach revolves around the brain’s intrinsic properties: neuroplasticity and the fact that the brain is neurodynamic. In our approach, neural organization and reorganization using natural or artificial environments aspires to bring computational perspectives into cognitive developmental neuroscience.     

Personal and impersonal stimuli differentially engage brain networks during moral reasoning

Moral decision making has recently attracted considerable attention as a core feature of all human endeavors. Previous functional magnetic resonance imaging studies about moral judgment have identified brain areas associated with cognitive or emotional engagement. Here, we applied graph theory-based network analysis of event-related potentials during moral decision making to reveal the personal/impersonal distinction in the organization of functional connectivity. Our results indicated that the personal task had more larger long-range connections involved in frontal regions and the right hemisphere, and higher network efficiency of some frontal electrodes such as F2 than the impersonal. These might be related to brain resource reorganization contributing to efficient conflict resolution. These findings provide new insights into neural mechanisms of moral dilemmas.     

Cognitive and affective development in adolescence

Questions about the nature of normative and atypical development in adolescence have taken on special significance in the last few years, as scientists have begun to recast old portraits of adolescent behavior in the light of new knowledge about brain development. Adolescence is often a period of especially heightened vulnerability as a consequence of potential disjunctions between developing brain, behavioral and cognitive systems that mature along different timetables and under the control of both common and independent biological processes. Taken together, these developments reinforce the emerging understanding of adolescence as a critical or sensitive period for a reorganization of regulatory systems, a reorganization that is fraught with both risks and opportunities.     

Preserved fronto-striatal plasticity and enhanced procedural learning in a transgenic mouse model of Alzheimer's disease overexpressing mutant hAPPswe

Mutations in the amyloid precursor protein (APP) gene inducing abnormal processing and deposition of beta-amyloid protein in the brain have been implicated in the pathogenesis of Alzheimer's disease (AD). Although Tg2576 mice with the Swedish mutation (hAPPswe) exhibit age-related Abeta-plaque formation in brain regions like the hippocampus, the amygdala, and the cortex, these mice show a rather specific deficit in hippocampal-dependent learning and memory tasks. In view of recent findings showing that neural systems subserving different forms of learning are not simply independent but that depressing or enhancing one system affects learning in another system, we decided to investigate fronto-striatal synaptic plasticity and related procedural learning in these mutants. Fronto-striatal long-term depression (LTD) induced by tetanic stimulation of the cortico-striatal input was similar in Tg2576 and wild-type control mice. Behavioral data, however, pointed to an enhancement of procedural learning in the mutants that showed robust motor-based learning in the cross maze and higher active avoidance scores. Thus, in this mouse model of AD, an intact striatal function associated with an impaired hippocampal function seems to provide neural conditions favorable to procedural learning. Our results suggest that focusing on preserved or enhanced forms of learning in AD patients might be of interest to describe the functional reorganization of the brain when one memory system is selectively compromised by neurological disease.     

The visual word form area: expertise for reading in the fusiform gyrus

Brain imaging studies reliably localize a region of visual cortex that is especially responsive to visual words. This brain specialization is essential to rapid reading ability because it enhances perception of words by becoming specifically tuned to recurring properties of a writing system. The origin of this specialization poses a challenge for evolutionary accounts involving innate mechanisms for functional brain organization. We propose an alternative account, based on studies of other forms of visual expertise (i.e. bird and car experts) that lead to functional reorganization. We argue that the interplay between the unique demands of word reading and the structural constraints of the visual system lead to the emergence of the Visual Word Form Area.     

The Importance of Sound for Cognitive Sequencing Abilities: The Auditory Scaffolding Hypothesis

ABSTRACT— Sound is inherently a temporal and sequential signal. Experience with sound therefore may help bootstrap—that is, provide a kind of "scaffolding" for—the development of general cognitive abilities related to representing temporal or sequential patterns. Accordingly, the absence of sound early in development may result in disturbances to these sequencing skills. In support of this hypothesis, we present two types of findings. First, normal-hearing adults do best on sequencing tasks when the sense of hearing, rather than sight, can be used. Second, recent findings suggest that deaf children have disturbances on exactly these same kinds of tasks that involve learning and manipulation of serial-order information. We suggest that sound provides an "auditory scaffolding" for time and serial-order behavior, possibly mediated through neural connections between the temporal and frontal lobes of the brain. Under conditions of auditory deprivation, auditory scaffolding is absent, resulting in neural reorganization and a disturbance to cognitive sequencing abilities.     

Why Fix What Isn't Broken? A Rejoinder to Ridenour,Daley, & Reich*

Ridenour, Daley, & Reich (2000) suggest that the Family Assessment Device should be reorganized. We disagree and provide further reasons why such a reorganization is unwise.     

Dynamic Relational Group Psychotherapy: A Neurobiologically Informed Model of Change

In this article, we introduce a preliminary, neurobiologically informed model of group therapy that links the timing and nature of specific group interventions with hypothesized changing neurobiological needs of the group. We suggest that the observed phases of group development reflect an underlying reorganization of neuronal circuitry that occurs as members progress through a hierarchically organized treatment, and that this reorganization involves the integration and homeostatic rebalancing of subcortical and neural networks. Our preliminary Dynamic Relational Model suggests that an understanding of the neurobiological processes involved in group development may help inform and direct effective group-based psychotherapy interventions.     

Event-related potentials in neuropsychological studies of language

Experiments are described in which event-related potentials (ERPs) are employed to study the specialization of functions between and within the cerebral hemispheres during the performance of language and nonlanguage tasks by normal adults. Similar studies of deaf subjects suggest that the functional organization of the brain may be altered after different early language and sensory experiences. Studies of patients with alexia without agraphia suggest that the ERP may be a valuable tool with which to study cerebral reorganization after brain damage.     

Language localization in cases of left temporal lobe arachnoid cyst: evidence against interhemispheric reorganization

We investigated whether left-hemisphere arachnoid cysts lead to reorganization of the language function using PET. A group analysis demonstrated that patients showed no more right-hemisphere activation than a matched control group. Several patients had clear language localizations in the left hemisphere during language comprehension; none of the patients showed right-hemisphere activation. We conclude that left-hemisphere tissue must suffer considerable compromise before reorganization of language into the right hemisphere becomes necessary. Language activations within the left hemisphere are clearly displaced. This is consistent with mere physical displacement in some patients rather than reorganization within the left hemisphere; in others intrahemispheric reorganization cannot be excluded.     

Attention,Memory, and Language after Pediatric Ischemic Stroke

A previous study evaluating receptive language after unilateral brain damage in childhood hypothesized lateralized attention and memory deficits without direct measurement. Our study directly measured attention, memory, and language in order to evaluate empirically the severity and laterality of sequelae. The performances of 11 individuals with a unilateral ischemic-lesion (7 right and 4 left hemisphere) were compared to controls matched on age, sex, and socioeconomic status. Results suggest subtle but persistent deficits in verbal memory, functional memory, and speed of processing after a lesion to either hemisphere. Lesions sustained before two years of age were associated with the lowest IQ scores. Our findings provide support for a configural representation of language that can to some extent compensate for inefficient or damaged components (Bates, 1994), and the middle-ground lateralization position (Thal et al., 1991) that asserts initial hemispheric specialization with the potential for reorganization.     

Training of School Psychologists in Neuropsychology and Brain Injury: Results of a National Survey of Training Programs

A previous study evaluating receptive language after unilateral brain damage in childhood hypothesized lateralized attention and memory deficits without direct measurement. Our study directly measured attention, memory, and language in order to evaluate empirically the severity and laterality of sequelae. The performances of 11 individuals with a unilateral ischemic-lesion (7 right and 4 left hemisphere) were compared to controls matched on age, sex, and socioeconomic status. Results suggest subtle but persistent deficits in verbal memory, functional memory, and speed of processing after a lesion to either hemisphere. Lesions sustained before two years of age were associated with the lowest IQ scores. Our findings provide support for a configural representation of language that can to some extent compensate for inefficient or damaged components (Bates, 1994), and the middle-ground lateralization position (Thal et al., 1991) that asserts initial hemispheric specialization with the potential for reorganization.     

Functional topography of early periventricular brain lesions in relation to cytoarchitectonic probabilistic maps

Early periventricular brain lesions can not only cause cerebral palsy, but can also induce a reorganization of language. Here, we asked whether these different functional consequences can be attributed to topographically distinct portions of the periventricular white matter damage. Eight patients with pre- and perinatally acquired left-sided periventricular brain lesions underwent focal transcranial magnetic stimulation to assess the integrity of cortico-spinal hand motor projections, and functional MRI to determine the hemispheric organization of language production. MRI lesion-symptom mapping revealed that two distinct portions of the periventricular lesions were critically involved in the disruption of cortico-spinal hand motor projections on the one hand and in the induction of language reorganization into the contra-lesional right hemisphere on the other hand. Both regions are located in a position compatible with the course of cortico-spinal/cortico-nuclear projections of the primary motor cortex in the periventricular white matter, as determined by the stereotaxic probabilistic cytoarchitectonic atlas developed by the Jülich group.     

How normal is grammatical development in the right hemisphere following hemispherectomy? The root infinitive stage and beyond

We examined the morphosyntax of eight left hemispherectomized children at two different stages and compared it to MLU-matched normals. We found that the language of the hemispherectomies paralleled that of their MLU matches with respect to the specific morphosyntactic characteristics of each stage. Our findings provide strong evidence for the presence of functional categories in all early grammars and demonstrate that grammatical development, regardless of its neural substrate, is highly constrained by UG and follows a narrowly determined course. We discuss our findings within a neurobiological framework in which etiology defines the integrity of the remaining hemisphere, which in turn, determines its potential for linguistic reorganization and/or acquisition.     

How does a child solve 7 + 8? Decoding brain activity patterns associated with counting and retrieval strategies

Cognitive development and learning are characterized by diminished reliance on effortful procedures and increased use of memory-based problem solving. Here we identify the neural correlates of this strategy shift in 7-9-year-old children at an important developmental period for arithmetic skill acquisition. Univariate and multivariate approaches were used to contrast brain responses between two groups of children who relied primarily on either retrieval or procedural counting strategies. Children who used retrieval strategies showed greater responses in the left ventrolateral prefrontal cortex; notably, this was the only brain region which showed univariate differences in signal intensity between the two groups. In contrast, multivariate analysis revealed distinct multivoxel activity patterns in bilateral hippocampus, posterior parietal cortex and left ventrolateral prefrontal cortex regions between the two groups. These results demonstrate that retrieval and counting strategies during early learning are characterized by distinct patterns of activity in a distributed network of brain regions involved in arithmetic problem solving and controlled retrieval of arithmetic facts. Our findings suggest that the reorganization and refinement of neural activity patterns in multiple brain regions plays a dominant role in the transition to memory-based arithmetic problem solving. Our findings further demonstrate how multivariate approaches can provide novel insights into fine-scale developmental changes in the brain. More generally, our study illustrates how brain imaging and developmental research can be integrated to investigate fundamental aspects of neurocognitive development.     

Motor excitability is reduced prior to voluntary movements in children and adolescents with Tourette syndrome

Tourette syndrome (TS) is a neuro‐developmental disorder characterized by the occurrence of motor and vocal tics: involuntary, repetitive, stereotyped behaviours that occur with a limited duration, often typically many times in a single day. Previous studies suggest that children and adolescents with TS may undergo compensatory, neuroplastic changes in brain structure and function that help them gain control over their tics. In the current study we used single‐pulse and dual‐site paired‐pulse transcranial magnetic stimulation (TMS), in conjunction with a manual choice reaction time task that induces high levels of inter‐manual conflict, to investigate this conjecture in a group of children and adolescents with TS, but without co‐morbid Attention Deficit Hyperactivity Disorder (ADHD). We found that performance on the behavioural response‐conflict task did not differ between the adolescents with TS and a group of age‐matched typically developing individuals. By contrast, our study demonstrated that cortical excitability, as measured by TMS‐induced motor‐evoked potentials (MEPs), was significantly reduced in the TS group in the period immediately preceding a finger movement. This effect is interpreted as consistent with previous suggestions that the cortical hyper‐excitability that may give rise to tics in TS is actively suppressed by cognitive control mechanisms. Finally, we found no reliable evidence for altered patterns of functional inter‐hemispheric connectivity in TS. These results provide evidence for compensatory brain reorganization that may underlie the increased self‐regulation mechanisms that have been hypothesized to bring about the control of tics during adolescence.     

Age-dependent consequences of seizures: relationship to seizure frequency, brain damage, and circuitry reorganization

Seizures in the developing brain pose a challenge to the clinician. In addition to the acute effects of the seizure, there are questions regarding the impact of severe or recurrent seizures on the developing brain. Whether provoked seizures cause brain damage, synaptic reorganization, or epilepsy is of paramount importance to patients and physicians. Such questions are especially relevant in the decision to treat or not treat febrile seizures, a common occurrence in childhood. These clinical questions have been addressed using clinical and animal research. The largest prospective studies do not find a causal connection between febrile seizures and later temporal lobe epilepsy. The immature brain seems relatively resistant to the seizure-induced neuronal loss and new synapse formation seen in the mature brain. Laboratory investigations using a developmental rat model corresponding to human febrile seizures find that even though structural changes do not result from hyperthermic seizures, synaptic function may be chronically altered. The increased understanding of the cellular and synaptic mechanisms of seizure-induced damage may benefit patients and clinicians in the form of improved therapies to attenuate damage and changes induced by seizures and to prevent the development of epilepsy.