Boom Chack Boom-A multimethod investigation of motor inhibition in professional drummers.

INTRODUCTION: Our hands are the primary means for motor interaction with the environment, and their neural organization is fundamentally asymmetric: While most individuals can perform easy motor tasks with two hands equally well, only very few individuals can perform complex fine motor tasks with both hands at a similar level of performance. The reason why this phenomenon is so rare is not well understood. Professional drummers represent a unique population to study it, as they have remarkable abilities to perform complex motor tasks with their two limbs independently. METHODS: Here, we used a multimethod neuroimaging approach to investigate the structural, functional, and biochemical correlates of fine motor behavior in professional drummers (n = 20) and nonmusical controls (n = 24). RESULTS: Our results show that drummers have higher microstructural diffusion properties in the corpus callosum than controls. This parameter also predicts drumming performance and GABA levels in the motor cortex. Moreover, drummers show less activation in the motor cortex when performing a finger-tapping task than controls. CONCLUSION: In conclusion, professional drumming is associated with a more efficient neuronal design of cortical motor areas as well as a stronger link between commissural structure and biochemical parameters associated with motor inhibition.

PLP1 Gene Variation Modulates Leftward and Rightward Functional Hemispheric Asymmetries.

Molecular neurobiological factors determining corpus callosum physiology and anatomy have been suggested to be one of the major factors determining functional hemispheric asymmetries. Recently, it was shown that allelic variations in two myelin-related genes, the proteolipid protein 1 gene PLP1 and the contactin 1 gene CNTN1, are associated with differences in interhemispheric integration. Here, we investigated whether three single nucleotide polymorphisms that were associated with interhemispheric integration via the corpus callosum in a previous study also are relevant for functional hemispheric asymmetries. To this end, we tested more than 900 healthy adults with the forced attention dichotic listening task, a paradigm to assess language lateralization and its modulation by cognitive control processes. Moreover, we used the line bisection task, a paradigm to assess functional hemispheric asymmetries in spatial attention. We found that a polymorphism in PLP1, but not CNTN1, was associated with performance differences in both tasks. Both functional hemispheric asymmetries and their modulation by cognitive control processes were affected. These findings suggest that both left and right hemisphere dominant cognitive functions can be modulated by allelic variation in genes affecting corpus callosum structure. Moreover, higher order cognitive processes may be relevant parameters when investigating the molecular basis of hemispheric asymmetries.

Cognitive Control Processes and Functional Cerebral Asymmetries: Association with Variation in the Handedness-Associated Gene LRRTM1.

Cognitive control processes play an essential role not only in controlling actions but also in guiding attentional selection processes. Interestingly, these processes are strongly affected by organizational principles of the cerebral cortex and related functional asymmetries, but the neurobiological foundations are elusive. We ask whether neurobiological mechanisms that affect functional cerebral asymmetries will also modulate effects of top-down control processes on functional cerebral asymmetries. To this end, we examined potential effects of the imprinted gene leucine-rich repeat transmembrane neuronal 1 (LRRTM1) on attentional biasing processes in a forced attention dichotic listening task in 983 healthy adult participants of Caucasian descent using the "iDichotic smartphone app." The results show that functional cerebral asymmetries in the language domain are associated with the rs6733871 LRRTM1 polymorphism when cognitive control and top-down attentional mechanisms modulate processes in bottom-up attentional selection processes that are dependent on functional cerebral asymmetries. There is no evidence for an effect of LRRTM1 on functional cerebral asymmetries in the language domain unrelated to cognitive control processes. The results suggest that cognitive control processes are an important factor to consider when being interested in the molecular genetic basis of functional cerebral architecture.

KIAA0319 promoter DNA methylation predicts dichotic listening performance in forced-attention conditions.

Language lateralization is one of the most prominent examples of functional hemispheric asymmetries. Previous studies indicate a significant contribution of factors not related to DNA sequence variation on the development of language lateralization, but the molecular processes underlying this relation are unclear. The Brandler-Paracchini model of hemispheric asymmetries assumes that genes involved in the establishment of ciliogenesis and bodily asymmetries also affect functional hemispheric asymmetries. Thus, genes implicated in this model represent a key target for epigenetic modulation of language lateralization. Here, we analyzed DNA methylation in the KIAA0319 (a gene involved in dyslexia and ciliogenesis) promoter region to investigate whether epigenetic markers of language lateralization can be identified in non-neuronal tissue. We found sex-specific effects of DNA methylation in single CpG sites on language lateralization in the forced-left (FL) and the forced-right (FR), but not on language lateralization in the non-forced (NF) condition of the dichotic listening task. These findings suggest that DNA methylation patterns in the KIAA0319 promoter region might be associated with cognitive control processes that are necessary to perform well in the forced-attention conditions. Furthermore, the assumption of an association between genes involved in ciliogenesis and the ontogenesis of functional hemispheric asymmetries is supported.

Asymmetric top-down modulation of ascending visual pathways in pigeons.

Cerebral asymmetries are a ubiquitous phenomenon evident in many species, incl. humans, and they display some similarities in their organization across vertebrates. In many species the left hemisphere is associated with the ability to categorize objects based on abstract or experience-based behaviors. Using the asymmetrically organized visual system of pigeons as an animal model, we show that descending forebrain pathways asymmetrically modulate visually evoked responses of single thalamic units. Activity patterns of neurons within the nucleus rotundus, the largest thalamic visual relay structure in birds, were differently modulated by left and right hemispheric descending systems. Thus, visual information ascending towards the left hemisphere was modulated by forebrain top-down systems at thalamic level, while right thalamic units were strikingly less modulated. This asymmetry of top-down control could promote experience-based processes within the left hemisphere, while biasing the right side towards stimulus-bound response patterns. In a subsequent behavioral task we tested the possible functional impact of this asymmetry. Under monocular conditions, pigeons learned to discriminate color pairs, so that each hemisphere was trained on one specific discrimination. Afterwards the animals were presented with stimuli that put the hemispheres in conflict. Response patterns on the conflicting stimuli revealed a clear dominance of the left hemisphere. Transient inactivation of left hemispheric top-down control reduced this dominance while inactivation of right hemispheric top-down control had no effect on response patterns. Functional asymmetries of descending systems that modify visual ascending pathways seem to play an important role in the superiority of the left hemisphere in experience-based visual tasks.

Distribution of serotonin 5-HT1A-binding sites in the brainstem and the hypothalamus, and their roles in 5-HT-induced sleep and ingestive behaviors in rock pigeons (Columba livia).

Serotonin 1A receptors (5-HT1ARs), which are widely distributed in the mammalian brain, participate in cognitive and emotional functions. In birds, 5-HT1ARs are expressed in prosencephalic areas involved in visual and cognitive functions. Diverse evidence supports 5-HT1AR-mediated 5-HT-induced ingestive and sleep behaviors in birds. Here, we describe the distribution of 5-HT1ARs in the hypothalamus and brainstem of birds, analyze their potential roles in sleep and ingestive behaviors, and attempt to determine the involvement of auto-/hetero-5-HT1ARs in these behaviors. In 6 pigeons, the anatomical distribution of [(3)H]8-OH-DPAT binding in the rostral brainstem and hypothalamus was examined. Ingestive/sleep behaviors were recorded (1h) in 16 pigeons pretreated with MM77 (a heterosynaptic 5-HT1AR antagonist; 23 or 69 nmol) for 20 min, followed by intracerebroventricular ICV injection of 5-HT (N:8; 150 nmol), 8-OH-DPAT (DPAT, a 5-HT1A,7R agonist, 30 nmol N:8) or vehicle. 5-HT- and DPAT-induced sleep and ingestive behaviors, brainstem 5-HT neuronal density and brain 5-HT content were examined in 12 pigeons, pretreated by ICV with the 5-HT neurotoxin 5,7-dihydroxytryptamine (5,7-DHT) or vehicle (N:6/group). The distribution of brainstem and diencephalic c-Fos immunoreactivity after ICV injection of 5-HT, DPAT or vehicle (N:5/group) into birds provided with or denied access to water is also described. 5-HT1ARs are concentrated in the brainstem 5-HTergic areas and throughout the periventricular hypothalamus, preoptic nuclei and circumventricular organs. 5-HT and DPAT produced a complex c-Fos expression pattern in the 5-HT1AR-enriched preoptic hypothalamus and the circumventricular organs, which are related to drinking and sleep regulation, but modestly affected c-Fos expression in 5-HTergic neurons. The 5-HT-induced ingestivebehaviors and the 5-HT- and DPAT-induced sleep behaviors were reduced by MM77 pretreatment. 5,7-DHT increased sleep per se, decreased tryptophan hydroxylase expression in the raphe nuclei and decreased prosencephalic 5-HT release but failed to affect 5-HT- or DPAT-induced drinking or sleep behavior. 5-HT- and DPAT-induced ingestive and sleep behaviors in pigeons appear to be mediated by heterosynaptic and/or non-somatodendritic presynaptic 5-HT1ARs localized to periventricular diencephalic circuits.

Visual asymmetries and the ascending thalamofugal pathway in pigeons.

The lateralized visual systems of pigeons and chickens are excellent models to study neural asymmetries at the functional and anatomical level. The aim of the current study was to reveal why these two species closely resemble each other with respect to left-right differences in behavior but not with respect to the pathways involved: While pigeons show an asymmetrically organized tectofugal system, only transient lateralizations of the thalamofugal system have been observed in chickens. Four possible explanations are conceivable. (1) Adult pigeons might also show a hitherto undiscovered thalamofugal asymmetry like chickens. (2) The thalamofugal asymmetry might be transient in both species. (3) Prehatch light stimulation could differentially affect the two visual pathways of chickens and pigeons that mature with different speeds. (4) Tecto- and thalamofugal asymmetries represent species differences, independent of developmental factors. To test these explanations, we injected retrograde tracers into the Wulst of adult pigeons, of hatchlings, and of dark reared pigeons which were monocularly deprived on their left or right eye for one week after hatch. Subsequently we counted labeled cells within the ipsi- and contralateral n. geniculatus lateralis pars dorsalis in search for possible lateralizations of ascending pathways. None of the experimental groups displayed significant differences in the thalamofugal projection pattern. This indicates that visual lateralization in pigeons and chickens depends on tectofugal and thalamofugal asymmetries, respectively. Thus, in different species a highly similar pattern of behavioral asymmetries can be subserved by diverse neural systems.

Recall deficits in stroke patients with thalamic lesions covary with damage to the parvocellular mediodorsal nucleus of the thalamus.

The functional role of the mediodorsal thalamic nucleus (MD) and its cortical network in memory processes is discussed controversially. While Aggleton and Brown (1999) suggested a role for recognition and not recall, Van der Werf et al. (2003) suggested that this nucleus is functionally related to executive function and strategic retrieval, based on its connections to the prefrontal cortices (PFC). The present study used a lesion approach including patients with focal thalamic lesions to examine the functions of the MD, the intralaminar nuclei and the midline nuclei in memory processing. A newly designed pair association task was used, which allowed the assessment of recognition and cued recall performance. Volume loss in thalamic nuclei was estimated as a predictor for alterations in memory performance. Patients performed poorer than healthy controls on recognition accuracy and cued recall. Furthermore, patients responded slower than controls specifically on recognition trials followed by successful cued recall of the paired associate. Reduced recall of picture pairs and increased response times during recognition followed by cued recall covaried with the volume loss in the parvocellular MD. This pattern suggests a role of this thalamic region in recall and thus recollection, which does not fit the framework proposed by Aggleton and Brown (1999). The functional specialization of the parvocellular MD accords with its connectivity to the dorsolateral PFC, highlighting the role of this thalamocortical network in explicit memory (Van der Werf et al., 2003).

Dichotic listening revisited: trial-by-trial ERP analyses reveal intra- and interhemispheric differences.

The dichotic listening (DL) paradigm is often used to assess brain asymmetries at the behavioral level. The aim of this study was to evaluate the dynamic temporal and topographical characteristics of event related potentials (ERPs) obtained with diotic and dichotic consonant-vowel (CV) stimuli from the same subjects. We used a novel approach in which we concurrently analyzed on a trial-by-trial basis ERP parameters during trials that resulted in a right ear advantage (REA) or left ear advantage (LEA) or that were presented under diotic (homonymous) conditions. CV syllables were used as auditory stimuli (/ba/, /da/, /ga/, /ka/, /pa/, /ta/). The EEG measurements were performed with 64 channels by mainly focusing on the N1P2, N2P3 and late negativity (LN) components. Overall, behavioral data revealed a clear REA. The central area showed higher amplitudes than the other locations for N1P2 responses. Additionally, responses were faster for the diotic, compared to the dichotic conditions. The LN had shorter latencies in trials resulting in a REA, compared with those producing a LEA. This result makes it likely that the overall REA is a time-bound effect, which can be explained by the structural theory of Kimura. Furthermore, the results demonstrated a specific spatiotemporal shift from central to frontal areas between N1P2 and LN that was pronounced in dichotic trials. This shift points towards the involvement of frontal areas in resolving conflicting input.

Increased cognitive functioning in symptomatic Huntington's disease as revealed by behavioral and event-related potential indices of auditory sensory memory and attention.

Cognitive functions are thought to deteriorate globally in late stages of various neurodegenerative disorders. Here we describe that this general assumption is not justified and fails in Huntington's disease (HD). Presymptomatic gene mutation carriers (pHDs) and healthy controls performed worse compared with symptomatic HDs in an auditory signal detection task. During task performance, behavioral data and event-related potentials (ERPs) [i.e., MMN (mismatch negativity), P3a, and RON (reorienting negativity)] were recorded. Not only behavioral performance but also neurophysiological correlates of auditory sensory memory and attentional reorientation indicate enhanced performance occurring primal in late stages of a neurodegenerative disorder. Increased activity of the NMDA-receptor system, an assumed pathogenic mechanism in HD, might facilitate signal propagation at striatal level that enables more efficient task execution through a winner-take-all process. The results challenge the view that late stage neurodegeneration is necessarily related to a global decline in cognitive abilities in HD. In contrast, selectively enhanced cognitive functioning can emerge together with otherwise impaired cognitive functioning.

Echoic memory in pigeons.

It is unknown whether birds are able to retain the memory of purely sensory auditory information such as white noise over an extended period of time. In a Pavlovian heart rate conditioning paradigm, four pigeons were trained to associate a mild electric shock with periodic random waveforms, and no shock with aperiodic noise. Periodic waveform detection requires echoic memory, i.e., the online retention of a waveform pattern over a limited time. Starting with 40ms, the waveform period was increased after successful learning until no significant stimulus discrimination could be found. Significant discrimination was achieved at periods of up to 2560ms. This is the first demonstration that echoic memory performance in birds is clearly superior to cats and gerbils, and comparable to naive human performance.

Calcium-binding proteins label functional streams of the visual system in a songbird.

The vertebrate nervous system has been shown to contain high concentrations of intracellular calcium-binding proteins, each of them with a restricted expression pattern in specific brain regions and specific neuronal subpopulations. Using immunohistochemical staining techniques, we analyzed the expression pattern of calbindin, calretinin and parvalbumin in visual brain areas of a songbird species, the zebra finch (Taeniopyga guttata). Here we show that the analyzed proteins are expressed in a complementary fashion within different brain substructures generally corresponding to functional subpathways of the avian visual system. In detail, calbindin is expressed in the brain structures that belong to the thalamofugal pathway, whereas parvalbumin-positive neurons are found in the brain structures that are part of the tectofugal visual pathway. Originally, the expression of calcium-binding proteins has been associated with specific morphological or neurochemical criteria of neurons. Our results suggest that their expression pattern also indicates a functional segregation of brain substructures linked to vision in the zebra finch brain. As the selective labeling of functional streams has also been shown for the visual system in mammalian species, function-selective expression of calcium-binding proteins might be a general feature of vertebrates.

Development of the diencephalic relay structures of the visual thalamofugal system in pigeons.

To compare the developmental pattern of the visual tecto- and thalamofugal pathways in the altricial pigeon, we examined the posthatch differentiation of the retinothalamic system. Choleratoxin was injected into the left and right eye to visualize the retinal innervation pattern of the lateral geniculate nucleus of the thalamus (GLd). The calcium-binding proteins parvalbumin and calbindin and GABA(Abeta) receptors were used as indicators for the functional development of the GLd. Although all retinorecipient thalamic target structures were invaded by retinal fibers directly after hatching, density of the projection increased during the first week. While the adult GLd was characterized by a substantial number of cells displaying calbindin-immunoreactivity and by a sparse innervation by parvalbumin-immunoreactive fibers, after hatching no labelling for calcium-binding proteins could be detected. Calbindin-immunoreactivity appeared not before posthatching day 7, while parvalbumin-immunoreactive fibers were detected only after the third week. In contrast, a dense but diffuse GABA(Abeta) receptor-labelling was present from hatching onwards that decreased during development. The delayed expression of calbindin as well as changes in the density of GABA(Abeta) receptors indicate that maturation of GLd neurons extends long into the posthatch period. It is likely that the GABAergic interneurons mainly develop within this posthatch timeframe. Combined with the delayed development of the parvalbumin-positive innervation, the developmental pattern of GLd neurons suggests that the thalamofugal networks are immature after hatching and therefore still sensitive to modulations of posthatch visual experience.

Creative thinking in adolescents with attention deficit hyperactivity disorder (ADHD).

A widened attentional focus, that is typically associated with ADHD, has been postulated to be accompanied by enhanced creative ability. However, creativity has been only limitedly examined in ADHD. Performance across several creativity measures were investigated in three groups: adolescents with ADHD, those with conduct disorder, and a healthy control sample. The ADHD group exhibited selective cognitive advantages and disadvantages by demonstrating an enhanced ability in overcoming the constraining influence of examples, but a reduced capacity to generate a functional invention during an imagery task. These findings are interpreted with reference to inhibitory control mechanisms and the contextual modulation of creative cognition.

Conceptual expansion and creative imagery as a function of psychoticism.

The ability to be creative is often considered a unique characteristic of conscious beings and many efforts have been directed at demonstrating a relationship between creativity and the personality construct of psychoticism. The present study sought to investigate this link explicitly by focusing on discrete facets of creative cognition, namely the originality/novelty dimension and the practicality/usefulness dimension. Based on Eysenck's conceptualisation of psychoticism as being characterised by an overinclusive cognitive style, it was expected that higher levels of psychoticism would accompany a greater degree of conceptual expansion and elevated levels of originality in creative imagery, but would be unrelated to the practicality/usefulness of an idea. These hypotheses were confirmed in 80 healthy participants who were contrasted based on their EPQ psychoticism scale scores. Our findings suggest that the link between psychoticism and creativity is based on associative thinking and broader but weak top-down activation patterns rather than on goal-related thinking.

Light experience induces differential asymmetry pattern of GABA- and parvalbumin-positive cells in the pigeon's visual midbrain.

The formation of functional and morphological asymmetries within the pigeon's tectofugal system depends on left-right differences in visual input during embryonic development. This asymmetric stimulation presumably affects activity-dependent differentiation processes within the optic tectum. Behavioral studies reveal that prehatch light stimulation asymmetry influences both left- and right-hemispheric processes in a differential way. Thus, we have to assume divergent effects on both hemispheres. This study represents an attempt to test the hypothesis that embryonic light asymmetry induces different, cell-type-specific effects in the left and the right optic midbrain. Since it is likely that inhibitory interneurons play a critical role in the establishment of asymmetries, we examined in both sides of the brain the soma sizes of GABA- and parvalbumin- (PV) immunoreactive (ir) cells of the tectum and the magnocellular isthmic nucleus in controls and in dark-incubated animals. No cell size asymmetries of magnocellular isthmic neurons were found in either dark-incubated or control birds. Dark-incubation also prevented the establishment of lateralized differences in GABAergic and PV-positive tectal cells. However, in control birds GABAergic cells displayed larger somata in the left tectum, whereas PV-ir neurons were enlarged within the right tectum. This complementary asymmetry pattern suggests that PV- and GABA-ir tectal cells represent different cellular populations which react differently to visual input. Thus, our data show that visual lateralization does not result from a mere growth promoting effect that enhances differentiation within the behaviorally dominant left side, but is constituted by different cell type-specific circuits which are divergently adjusted in the left and in the right tectum.