Semantic processing of neglected numbers

While neglected stimuli can still be processed, few studies have directly addressed the issue of the unconscious access to semantics. In order to clarify this issue, we engaged four patients with unilateral left spatial neglect in a number comparison task. Each target number was preceded by a lateralized number prime, either in the intact or neglected hemifield (HF). Both group analyses and the intensive study of a single patient show that left (neglected) as well as right (consciously perceived) number primes affect performance: primes representing quantities that fall on the same side of the reference as the target lead to faster categorization. This congruency effect is highly suggestive of numerical semantic processing of neglected stimuli. Absence of conscious perception of neglected primes was evaluated using a combination of subjective and objective measures of performance in forced-choice tasks.     

Abstruse neologism formation: parallel processing revisited

Aspects of two different approaches to normal syllable formation (Berg, 1989; Clements, 1988, 1990) are incorporated into a model of abstruse neologism production characterized by redundant coding of sonority at various levels of parallel language processing. Data suggesting that the sonority profiles of abstruse neologisms accord with patterns found in legitimate English words are presented. Discussion explores neologism genesis from two well-known theoretical perspectives, illustrates how each theory of syllable formation might be instantiated within the model, and illustrates the role of sonority in constraining abstruse neologism production at several levels of parallel processing.     

Modeling the functional organization of the basal ganglia. A parallel distributed processing approach

Despite recent advances in the understanding of the pathophysiology of movement disorders, little is known about the precise function the basal ganglia play in the control of movement. We review an approach to studying the function of neural systems that is based on the use of a class of computer models known as parallel distributed processors (PDPs) and indicate its potential range of applications to the study of movement disorders. PDPs can be used to construct computational devices that take into account the anatomical and pharmacological properties of real neural systems. They can also provide computational-level insights that can lead to novel hypotheses concerning brain function. We discuss both these approaches and outline a scheme of the functional organization of the basal ganglia, which predicts some of the pathophysiological mechanisms that mediate movement disorders and which can be formally modeled on a computer.     

Bilateral hemispheric processing deficits in schizophrenia

Schizophrenics are known to have an early visual processing deficit, but the exact nature of that deficit is unclear. The present research was undertaken in order to establish the difference between schizophrenic and normal subjects in their processing of visual stimuli. Previous studies have shown that short duration stimuli activate a transient visual system which is associated with the right hemisphere, while longer duration stimuli activate the sustained system associated with the left hemisphere. The present study was designed to determine the effects of activation/inactivation of both the sustained and transient channels on hemispheric processing in normal compared to schizophrenic patients. The task was a forced choice continuity of form. The subject was required to detect two grating pulses, separated by a blank interval (interstimulus interval-ISI) vs. a single grating pulse, which was shown for the same total duration as the two pulse condition. Threshold ISI was obtained and used as the index of visible persistence/speed of visual processing, 19 schizophrenics, 12 depressives, 6 schizoaffectives, and 11 controls participated in the study. Stimuli were sinusoidal spatial frequency (SF) gratings of 0.9 and 15 c/degrees presented independently to the left and right hemisphere for durations of 50 and 250 ms. The results revealed statistical significance for Diagnosis, Diagnosis x SF, and Position x Diagnosis. Normal controls and depressed subjects did not statistically differ from each other, while schizophrenic and schizoaffectives differed from both control groups and on some conditions from each other. No hemispheric asymmetries were observed for any group. The results are discussed in terms of differential deficits in schizophrenics in the absence of early occurring asymmetries.     

Clinical trials in migraine: parallel versus crossover studies

Most prophylactic drug studies for migraine utilize parallel or crossover formats. Both study designs have disadvantages and advantages. The pros and contras of each study are discussed. The majority of headache investigators seem to favor the parallel study and reasons for this preference are discussed.     

The nonintentional processing of Arabic numbers in children

This paper aims at determining when magnitude is automatically activated from Arabic digits in children and whether this automatic activation depends on the number size of the stimuli considered. Second, third, and fourth graders performed a physical Stroop task in which pairs of single- and two-digit Arabic numerals in a ratio 1:2 or 2:3 were used. In addition, the speed of perceptual and semantic information was balanced: Instead of presenting the two members of each pair directly with a physical size difference, they first appeared in the same intermediate physical size, the perceptual difference occurring only after some time. The results indicated a significant effect of congruity at all grades, with faster reaction times and lower error rates for congruent trials than for incongruent trials, for both one- and two-digit numerals. Furthermore, this congruity effect was affected by the ratio of the numbers in the pairs. Only pairs of ratio 1:2 were affected by this congruity effect. These findings strongly support the fact that children as young as 7 years old can automatically access the magnitude information of one- as well as two-digit Arabic numerals.     

Bilateral processing of redundant information: the influence of stimulus notation and processing speed in number comparison

Improved performance is generally observed when identical copies of a stimulus are presented bilaterally to both visual half fields (VHFs), relative to unilateral single presentations. We investigated the influence of stimulus notation and processing speed on this bilateral redundancy gain (B-RG) in number comparison. Two experiments were performed with consistent (i.e., two identical copies of Arabic digits or word numerals) and inconsistent (i.e., an Arabic digit in one VHF with a word numeral of the same value in the other VHF) displays (see also Marks and Hellige, 2003 for a similar design in number naming). In Experiment 1, the processing speeds of the Arabic digits were faster than the ones of the word numerals while in Experiment 2, the processing speeds of the two stimulus notations were kept equal. A significant difference between consistent and inconsistent conditions was restricted to Experiment 1 in which the processing speeds of the two stimulus notations diverged. These results are discussed in the framework of a simple race model in which two independent hemispheric processes compete for the control of response, and the faster process wins.     

Hemispheric differences for visual search: Serial vs parallel processing revisited

Subjects were tachistoscopically presented with arrays of two, three or four stimuli to the right or left hemisphere and judged whether all of the items were the same or whether one was physically different from the rest. Separate groups of right-handed subjects viewed letters of featurally similar symbols as stimulus items. Faster and more accurate responding was obtained for left hemisphere presentations for both same and different response judgments. Response time was independent of array size, with same judgments made faster than different judgments for both visual field conditions. Extensive practice shortened reaction time and decreased error rate, but did not change the pattern of hemispheric or judgment effects. Virtually identical results were observed for both stimulus conditions. These findings suggest that the left hemisphere can process information in parallel when the task situation requires featural analysis of stimulus materials.     

Analog numerical representations in rhesus monkeys: evidence for parallel processing

Monkeys have been introduced as model organisms to study neural correlates of numerical competence, but many of the behavioral characteristics of numerical judgments remain speculative. Thus, we analyzed the behavioral performance of two rhesus monkeys judging the numerosities 1 to 7 during a delayed match-to-sample task. The monkeys showed similar discrimination performance irrespective of the exact physical appearance of the stimuli, confirming that performance was based on numerical information. Performance declined smoothly with larger numerosities, and reached discrimination threshold at numerosity "4." The nonverbal numerical representations in monkeys were based on analog magnitudes, object tracking process ("subitizing") could not account for the findings because the continuum of small and large numbers shows a clear Weber fraction signature. The lack of additional scanning eye movements with increasing set sizes, together with indistinguishable neuronal response latencies for neurons with different preferred numerosities, argues for parallel encoding of numerical information. The slight but significant increase in reaction time with increasing numerosities can be explained by task difficulty and consequently time-consuming decision processes. The behavioral results are compared to single-cell recordings from the prefrontal cortex in the same subjects. Models for numerosity discrimination that may account for these results are discussed.     

Functional architecture of basal ganglia circuits: neural substrates of parallel processing.

Concepts of basal ganglia organization have changed markedly over the past decade, due to significant advances in our understanding of the anatomy, physiology and pharmacology of these structures. Independent evidence from each of these fields has reinforced a growing perception that the functional architecture of the basal ganglia is essentially parallel in nature, regardless of the perspective from which these structures are viewed. This represents a significant departure from earlier concepts of basal ganglia organization, which generally emphasized the serial aspects of their connectivity. Current evidence suggests that the basal ganglia are organized into several structurally and functionally distinct 'circuits' that link cortex, basal ganglia and thalamus, with each circuit focused on a different portion of the frontal lobe. In this review, Garrett Alexander and Michael Crutcher, using the basal ganglia 'motor' circuit as the principal example, discuss recent evidence indicating that a parallel functional architecture may also be characteristic of the organization within each individual circuit.     

Hippocampal-prefrontal dynamics in spatial working memory: interactions and independent parallel processing

Memory processes may be independent, compete, operate in parallel, or interact. In accordance with this view, behavioral studies suggest that the hippocampus (HPC) and prefrontal cortex (PFC) may act as an integrated circuit during performance of tasks that require working memory over longer delays, whereas during short delays the HPC and PFC may operate in parallel or have completely dissociable functions. In the present investigation we tested rats in a spatial delayed non-match to sample working memory task using short and long time delays to evaluate the hypothesis that intermediate CA1 region of the HPC (iCA1) and medial PFC (mPFC) interact and operate in parallel under different temporal working memory constraints. In order to assess the functional role of these structures, we used an inactivation strategy in which each subject received bilateral chronic cannula implantation of the iCA1 and mPFC, allowing us to perform bilateral, contralateral, ipsilateral, and combined bilateral inactivation of structures and structure pairs within each subject. This novel approach allowed us to test for circuit-level systems interactions, as well as independent parallel processing, while we simultaneously parametrically manipulated the temporal dimension of the task. The current results suggest that, at longer delays, iCA1 and mPFC interact to coordinate retrospective and prospective memory processes in anticipation of obtaining a remote goal, whereas at short delays either structure may independently represent spatial information sufficient to successfully complete the task.     

Effective connectivity during processing of facial affect: evidence for multiple parallel pathways

The perception of facial affect engages a distributed cortical network. We used functional magnetic resonance imaging and dynamic causal modeling to characterize effective connectivity during explicit (conscious) categorization of affective stimuli in the human brain. Specifically, we examined the modulation of connectivity from posterior regions of the face-processing network to the lateral ventral prefrontal cortex (VPFC) during affective categorization and we tested for a potential role of the amygdala (AMG) in mediating this modulation. We found that explicit processing of facial affect led to prominent modulation (increase) in the effective connectivity from the inferior occipital gyrus (IOG) to the VPFC, while there was less evidence for modulation of the afferent connections from fusiform gyrus and AMG to VPFC. More specifically, the forward connection from IOG to the VPFC exhibited a selective increase under anger (as opposed to fear or sadness). Furthermore, Bayesian model comparison suggested that the modulation of afferent connections to the VPFC was mediated directly by facial affect, as opposed to an indirect modulation mediated by the AMG. Our results thus suggest that affective information is conveyed to the VPFC along multiple parallel pathways and that AMG activity is not sufficient to account for the gating of information transfer to the VPFC during explicit emotional processing.     

Organic versus functional etiology in catatonia: case report

The case of an illegal alien brought to the emergency room in a catatonic stupor is described. The patient's condition worsened following the administration of a high-potency neuroleptic, and it was later learned that he had a history of epileptic seizures. This case emphasizes the importance of ruling out organic causes in patients presenting with catatonic symptoms.     

基于癫痫患者皮质-皮质诱发电位的双侧岛叶功能连接研究(附四例报告)

目的通过立体脑电图电极皮质电刺激的方法探讨岛叶或岛叶相关药物难治性癫痫患者双侧岛叶之间的功能连接情况。方法回顾性分析2014年1月至2016年8月清华大学玉泉医院癫痫中心收治的4例岛叶或岛叶相关药物难治性癫痫患者的临床资料。4例患者均于双侧岛叶植入立体脑电图电极进行皮质电刺激,通过视觉分析和非参数检验确定每个触点有无诱发电位响应。采用刺激一侧的对侧岛叶的电极记录诱发电位响应,明确刺激响应率及解剖分布情况。结果4例患者共植入28根SEEG电极(98个触点),其中植入左侧岛叶12根电极(47个触点)。4例患者的双侧岛叶之间有皮质-皮质诱发电位(CCEP)响应。刺激一侧岛叶时,对侧岛叶CCEP的响应率为39.8%,峰潜伏期为15.5~196.0ms。此外,在双侧岛叶等位脑回间存在双向CCEP联系。结论岛叶或岛叶相关的难治性癫痫患者的双侧岛叶之间存在双向功能连接,特别是病毒性脑炎后癫痫患者,其双侧岛叶之间的连接更为广泛。但这一结果尚需更多病例来进一步证实。