Cognition in schizophrenia: core psychological and neural mechanisms

The challenge in understanding cognitive impairment in schizophrenia is that people with this illness have deficits in an array of domains. Here, we briefly review evidence regarding the pattern of deficits within three domains: context processing, working memory and episodic memory. We suggest that there may be a common mechanism driving deficits in these domains - an impairment in the ability to actively represent goal information in working memory to guide behavior, a function we refer to as proactive control. We suggest that such deficits in proactive control reflect impairments in dorsolateral prefrontal cortex, its interactions with other brain regions, such as parietal cortex, thalamus and striatum, and the influence of neurotransmitter systems, such as dopamine, GABA and glutamate.     

Animal Learning and Cognition: A neural network approach

by Nestor A. Schmajuk, Cambridge University Press, 1997. ￡29.95 (xii+340 pages) ISBN 0 521 45086 1.     

Dissociable neural systems of sequence learning

Although current theories all point to distinct neural systems for sequence learning, no consensus has been reached on which factors crucially define this distinction. Dissociable judgment-linked versus motor-linked and implicit versus explicit neural systems have been proposed. This paper reviews these two distinctions, yet concludes that these traditional dichotomies prove insufficient to account for all data on sequence learning and its neural organization. Instead, a broader theoretical framework is necessary providing a more continuous means of dissociating sequence learning systems. We argue that a more recent theory, dissociating multidimensional versus unidimensional neural systems, might provide such framework, and we discuss this theory in relation to more general principles of associative learning and recent imaging findings.     

Dissociable neural systems for recognizing emotions

This study tested the hypothesis that the recognition of emotions would draw upon anatomically separable brain regions, depending on whether the stimuli were static or explicitly conveyed information regarding actions. We investigated the hypothesis in a rare subject with extensive bilateral brain lesions, patient B., by administering tasks that assessed recognition and naming of emotions from visual and verbal stimuli, some of which depicted actions and some of which did not. B. could not recognize any primary emotion other than happiness, when emotions were shown as static images or given as single verbal labels. By contrast, with the notable exception of disgust, he correctly recognized primary emotions from dynamic displays of facial expressions as well as from stories that described actions. Our findings are consistent with the idea that information about actions is processed in occipitoparietal and dorsal frontal cortices, all of which are intact in B.'s brain. Such information subsequently would be linked to knowledge about emotions that depends on structures mapping somatic states, many of which are also intact in B.'s brain. However, one of these somatosensory structures, the insula, is bilaterally damaged, perhaps accounting for B.'s uniformly impaired recognition of disgust (from both static and action stimuli). Other structures that are damaged in B.'s brain, including bilateral inferior and anterior temporal lobe and medial frontal cortices, appear to be critical for linking perception of static stimuli to recognition of emotions. Thus the retrieval of knowledge regarding emotions draws upon widely distributed and partly distinct sets of neural structures, depending on the attributes of the stimulus.     

Acetylcholine modulation of neural systems involved in learning and memory

Extensive evidence supports the view that cholinergic mechanisms modulate learning and memory formation. This paper reviews evidence for cholinergic regulation of multiple memory systems, noting that manipulations of cholinergic functions in many neural systems can enhance or impair memory for tasks generally associated with those neural systems. While parallel memory systems can be identified by combining lesions with carefully crafted tasks, most—if not all—tasks require the combinatorial participation of multiple neural systems. This paper offers the hypothesis that the magnitude of acetylcholine (ACh) release in different neural systems may regulate the relative contributions of these systems to learning. Recent studies of ACh release, obtained with in vivo microdialysis samples during training, together with direct injections of cholinergic drugs into different neural systems, provide evidence that release of ACh is important in engaging these systems during learning, and that the extent to which the systems are engaged is associated with individual differences in learning and memory.     

Understanding the emergence of modularity in neural systems

Modularity in the human brain remains a controversial issue, with disagreement over the nature of the modules that exist, and why, when, and how they emerge. It is a natural assumption that modularity offers some form of computational advantage, and hence evolution by natural selection has translated those advantages into the kind of modular neural structures familiar to cognitive scientists. However, simulations of the evolution of simplified neural systems have shown that, in many cases, it is actually non-modular architectures that are most efficient. In this paper, the relevant issues are discussed and a series of simulations are presented that reveal crucial dependencies on the details of the learning algorithms and tasks that are being modelled, and the importance of taking into account known physical brain constraints, such as the degree of neural connectivity. A pattern is established which provides one explanation of why modularity should emerge reliably across a range of neural processing tasks.     

Affect and Cognition

ABSTRACT— One of the greatest puzzles of human nature concerns the poorly understood interplay between affect and cognition—the rational and emotional ways of dealing with the social world around us. Affect is a ubiquitous and powerful phenomenon in our lives, yet research on human affectivity has been neglected until quite recently. This article reviews traditional and contemporary approaches to this issue, and recent theoretical and empirical work exploring the links between affect and cognition is considered. The major achievements and shortcomings of this now-thriving research area are discussed, and the future prospects of psychological research on human affectivity are considered.     

基础认知与社会认知中内隐过程及其脑机制*

认知过程及其脑机制是心理学研究的重要内容。社会认知是人们在社会生活中对他人行为的意图及情感的认识,是人际互动的重要方面,具有深刻的理论和实践意义。本文全面深入地对社会认知和基础认知中自动加工过程进行了研究综述,对基础认知与社会认知的研究方式进行了比较。自动加工过程是社会认知和基础认知中都存在的重要过程,从脑机制研究角度,相关的电生理学指标(如N400等)都可以作为研究的指标来考察社会认知中的自动加工过程。本文从社会认知与基础认知的比较入手,介绍了各种领域的研究方法,特别是事件相关电位技术等认知神经科学研究方法。     

Dissociable neural systems support retrieval of how and why action knowledge

In everyday discourse, people typically represent actions in one of two ways: how they are performed or why they are performed. In the present study, we determined the neural systems that support these natural modes of representing actions. Participants underwent functional magnetic resonance imaging while identifying how and why people perform various familiar actions. Identifying how actions are performed produced activity in premotor areas that support the execution of actions and in higher-order visual areas that support the perception of action-related objects; this finding supports an embodied view of action knowledge. However, identifying why actions are performed preferentially engaged areas of the brain associated with representing and reasoning about mental states; these areas were right temporoparietal junction, precuneus, dorsomedial prefrontal cortex, and posterior superior temporal sulcus. Our results suggest that why action knowledge is not sufficiently constituted by information in motor and visual systems, but requires a system for representing states of mind, which do not have reliable motor correlates or visual appearance.     

Animal Cognition: The Bridge BetweenAnimal Learning and Human Cognition

Carefully controlled research with animals has demonstrated cognitive capacities for which traditional theories of associative learning cannot account. One example is the symbolic representation of stimuli. If two arbitrary stimuli are associated with a third event, an emergent relation can be shown to develop. A second example is the ability of animals to plan ahead, and to choose whether to plan ahead or not. Although animals have often been used to model drug effects in humans, these models have rarely been used to examine the effects of drugs on cognitive functioning. Furthermore, examination of the effects of drugs on the cognitive behavior of animals may help to identify the nature of the representations underlying the cognition.     

Towards a functional neural systems model of developmental stuttering

This paper overviews recent developments in an ongoing program of brain imaging research on developmental stuttering that is being conducted at the University of Texas Health Science Center, San Antonio. This program has primarily used H₂¹⁵O PET imaging of different speaking tasks by right-handed adult male and female persistent stutterers, recovered stutterers and controls in order to isolate the neural regions that are functionally associated with stuttered speech. The principal findings have emerged from studies using condition contrasts and performance correlation techniques. The emerging findings from these studies are reviewed and referenced to a neural model of normal speech production recently proposed by Jürgens [Neurosci. Biobehav. Rev. 26 (2002) 235]. This paper will report (1) the reconfiguration of previous findings within the Jürgens Model; (2) preliminary findings of an investigation with late recovered stutterers; (3) an investigation of neural activations during a treatment procedure designed to produce a sustained improvement in fluency; and (4) an across-studies comparison that seeks to isolate neural regions within the Jürgens Model that are consistently associated with stuttering. Two regions appear to meet this criterion: right anterior insula (activated) and anterior middle and superior temporal gyri (deactivated) mainly in right hemisphere. The implications of these findings and the direction of future imaging investigations are discussed.

Educational objectives: The reader will learn about (1) recent uses of H₂¹⁵O PET imaging in stuttering research; (2) the use of a new neurological model of speech production in imaging research on stuttering; and (3) initial findings from PET imaging investigations of treated and recovered stutterers.     

Culture and Causal Cognition

East Asian and American causal reasoning differs significantly. East Asians understand behavior in terms of complex interactions between dispositions of the person or other object and contextual factors, whereas Americans often view social behavior primarily as the direct unfolding of dispositions. These culturally differing causal theories seem to be rooted in more pervasive, culture-specific mentalities in East Asia and the West. The Western mentality is analytic, focusing attention on the object, categorizing it by reference to its attributes, and ascribing causality based on rules about it. The East Asian mentality is holistic, focusing attention on the field in which the object is located and ascribing causality by reference to the relationship between the object and the field.     

Cognition and hearing aids

The perceptual information transmitted from a damaged cochlea to the brain is more poorly specified than information from an intact cochlea and requires more processing in working memory before language content can be decoded. In addition to making sounds audible, current hearing aids include several technologies that are intended to facilitate language understanding for persons with hearing impairment in challenging listening situations. These include directional microphones, noise reduction, and fast-acting amplitude compression systems. However, the processed signal itself may challenge listening to the extent that with specific types of technology, and in certain listening situations, individual differences in cognitive processing resources may determine listening success. Here, current and developing digital hearing aid signal processing schemes are reviewed in the light of individual working memory (WM) differences. It is argued that signal processing designed to improve speech understanding may have both positive and negative consequences, and that these may depend on individual WM capacity.