PET detects changes in metabolism between task periods and is thus insensitive to areas that are activated during all or most of cognition. Depth-recorded, evokedpotentials indicate that many multimodal and limbic cortical areas may be activated during most cognitive tasks. Thus, PET may be insensitive to some core processes of awareness that are difficult to eliminate from the control periods.

A model of the neuropsychology of anxiety is proposed. The model is based in the first instance upon an analysis of the behavioural effects of the antianxiety drugs in animals. From such psychopharmacologi-cal experiments the concept of a “behavioural inhibition system” has been developed. This system responds to novel stimuli or to those associated with punishment or nonreward by inhibiting ongoing behaviour and increasing arousal and attention to the environment. It is activity in the BIS that constitutes anxiety and that (...) is reduced by antianxiety drugs. The effects of the antianxiety drugs in the brain also suggest hypotheses concerning the neural substrate of anxiety. Although the benzodiazepines and barbiturates facilitate the effects of γ-aminobutyrate, this is insufficient to explain their highly specific behavioural effects. Because of similarities between the behavioural effects of certain lesions and those of the antianxiety drugs, it is proposed that these drugs reduce anxiety by impairing the functioning of a widespread neural system including the septo-hippocampal system, the Papez circuit, the prefrontal cortex, and ascending monoaminergic and cholinergic pathways which innervate these forebrain structures. Analysis of the functions of this system suggests that it acts as a comparator: it compares predicted to actual sensory events and activates the outputs of the BIS when there is a mismatch or when the predicted event is aversive. Suggestions are made as to the functions of particular pathways within this overall brain system. The resulting theory is applied to the symptoms and treatment of anxiety in man, its relations to depression, and the personality of individuals who are susceptible to anxiety or depression. (shrink)

On the basis of neuroiinaging studies, Posner & Raichle summarily report that the prefrontal cortex is involved in executive functioning and attention. In contrast to that superficial view, we briefly describe a testable model of the kinds of representations that are stored in prefrontal cortex, which, when activated, are expressed via plans, actions, thematic knowledge, and schemas.

Research reported by Posner & Raichle may be usefully applied to the rehabilitation of persons with brain damage. Their findings are related to the “dual premotorsystems hypothesis” that reciprocally interactive medial and lateral brain systems are involved in attention and learning. Recent studies show that “brain healing” occurs through dynamic reorganization involving attentional networks postulated by Posner & Raichle.

Images of mindis an exciting book, well-written and wellorganized, but many of the connections the authors draw between PET scan results and more general psychological issues are somewhat strained.

The literature on time perception is discussed. This is done with reference both to the ''cognitive-timer'' model for time estimation and to the subjective experience of apparent duration. Three assumptions underlying the model are scrutinized. I stress the strong interplay among attention, arousal, and time perception, which is at the base of the cognitive-timer model. It is suggested that a multiplicative function of two key components (the number of subjective time units and their size) should predict apparent duration. Implications for (...) other cognitive domains are drawn, and in particular an analogy is suggested between apparent duration and apparent movement. (shrink)

The present issue of Cognition and Emotion represents a laudable project: publication of some current research and theoretical orientations on two important topics that have not received the attent...

The approach adopted by Posner & Raichle in this book, with its strong emphasis on the cognitive level of description, is ideally suited to the study of psychotic illnesses. However, their discussion of depression and schizophrenia is based on a very small number of studies and involves ad hoc arguments derived largely from neuroanatomy. Their conclusions are almost certainly wrong.

Posner & Raichle's book presents methods and data that increase support for mind-brain unity and provide a method for studying and verifying brain dysfunction objectively. Their incorporation into the assessment technology of neuropsychology should accordingly constitute a major advance. In addition, these techniques may help clarify longstanding controversies in cognitive psychology such as whether perception is multimodal or amodal.

Encoding articulate speech is widely accepted as the principal (or sole) role of the frontal operculum. Clinical observations of speech apraxia have been confirmed by brain-imaging studies of speech production. We present evidence that the frontal operculum also programs limb movements. We argue that this area is a ventral counterpart of the dorsal premotor area. The two are functionally distinguished by specialization for somatic and visual space, respectively.

A methodological problem may distort the implications derived from the metabolism scans of the brain, but Posner & Raichle may have found neural networks which underlie the analytical and synthetical hemispheric data processing mechanism. This methodological problem is that a large regional consumption of energy, detected by the PET technique, is not necessarily related to more data processing. It may be related to the inefficiency of the neural system at this region.

The idea of arousal as a non-specific state of activation has been implicated as an explanatory factor for many aspects of human behavior, ranging from emotional experiences to learning and memory. Critiques of this concept have highlighted that arousal is ambiguous and evidence for its role in emotion is mixed. However, contemporary emotion theories and empirical research continue to incorporate the concept of arousal in ways that fail to address its problems. Here, we review the origins of the term arousal (...) in physiology and trace how it has been translated and applied to psychology (particularly as it relates to emotion). We consider whether the construct of arousal is currently (a) consistent and (b) useful in understanding human behavior. (shrink)

Images of mindmarks a new era in human cognitive neuroscience. Despite the difficult conceptual problems associated with using group-averaged data and paired subtractions, human PET images converge well with existing data from other areas of cognitive neuroscience while opening up new theoretical and experimental possibilities. However, greater attention to individual differences might prove necessary in the study of culturally driven adaptations such as literacy.

To understand the endogenous components of the event-related brain potential (ERP), we must use data about the components' antecedent conditions to form hypotheses about the information-processing function of the underlying brain activity. These hypotheses, in turn, generate testable predictions about the consequences of the component. We review the application of this approach to the analysis of the P300 component. The amplitude of the P300 is controlled multiplicatively by the subjective probability and the task relevance of the eliciting events, whereas its (...) latency depends on the duration of stimulus evaluation. These and other factors suggest that the P300 is a manifestation of activity occurring whenever one's model of the environment must be revised. Tests of three predictions based on this “context updating” model are reviewed. Verleger's critique is based on a misconstrual of the model as well as a partial and misleading reading of the relevant literature. (shrink)

Extraversion has two central characteristics: (1) interpersonalengagement, which consists of affiliation (enjoying and valuing close interpersonal bonds, being warm and affectionate) and agency (being socially dominant, enjoying leadership roles, being assertive, being exhibitionistic, and having a sense of potency in accomplishing goals) and (2) impulsivity, which emerges from the interaction of extraversion and a second, independent trait (constraint). Agency is a more general motivational disposition that includes dominance, ambition, mastery, efficacy, and achievement. Positive affect (a combination of positive feelings and (...) motivation) is closely associated with extraversion. Extraversion is accordingly based on positiveincentivemotivation. (shrink)

In interpreting measurements of brain processes it is necessary to make the model used explicit. A concept such as attention cannot be used in the description of brain activities without a model of the relation of mental and neural processes.

This book delivers much more than its title appears to promise; it is not merely a description of current methods for remotely monitoring brain activity. It primarily concentrates on just one such method: positron emission tomography, but it demonstrates beautifully how far that technique can now take us in the quest to discover the mechanisms underlying thought.

Posner & Raichle's (1994) exciting, wonderfully illustrated book describes the past successes and future potential of the relatively noninvasive imaging of the nervous systems of living people. The focus has been on cognitive processes but there is no reason why emotional and motivational systems cannot also be tapped. Although the authors do not formally address such contentious issues as consciousness and the private experience of other species, imaging methods may hold promise for helping us to understand these phenomena, as well (...) as to integrate psychological processes into ethological and phylogenetic research in general. (shrink)

The principles of classical and quantum holography are used to develop the theoretical basis for a non-phonemic method of detecting membership in secret social groups, such as cults, criminal gangs, drug cartels, and terrorist cells. Grounded in the basic sociological premise that every group develops a distinctive sociocultural order, the theory postulates that the primary features of a group's collective identity will be encoded, via a multilevel socio-psycho-physiological process, into the field of bio-emotional relations connecting group members. The principles of (...) classical holography (Gabor 1948) are used to describe how this information is recorded in the members' brains and communicated in interaction by a holographic-like process as a tacit signature of group affiliation —a constancy in group-related interactions. It is hypothesized that the identity signature is enfolded as a hologram in the energy spectra of vocal interactions among group members. The principles of quantum holography (Gabor 1946) are used to provide a description of the group's ongoing interactions as a dynamic process—a continuous, quantized series of snapshots (quantum holograms). Linked together, two forms of holography provide a model of how the group's collective identity evolves and is communicated over time to its members, as the group adapts to the ever-changing reality of its endogenous and exogenous circumstances. Using spectral analysis techniques, it should be possible to detect the group's identity signature in the recordings of relatively small samples of vocal interactions. In clandestine groups, the effort to remain hidden actually enhances the signal strength of the identity signature. It is predicted, therefore, that detection of unknown members can be achieved by using the spectral commonality identified in the analysis of recordings of vocal interactions among known members as a reference signature for comparison with those of the vocal spectra of suspected or potential members. (shrink)