Plasticity of the callosal system

A series of experiments examined the potential plasticity of the callosal system in both epileptic patients and in kittens submitted to corpus callosotomy at various ages. The patients were tested for unilateral discrimination and interhemispheric transfer of tactile information. The youngest patient was also required to perform additional inter- and intrahemispheric comparisons of visual and tactile stimuli. The animals were tested for interhemispheric transfer of visual discriminations. The results suggest that in both animals and humans there exists a critical period before which callosal section does not disrupt interhemispheric communication. The results also indicate that the compensatory mechanisms used to achieve interhemispheric transfer in the absence of the corpus callosum may vary according to the sensory modality involved. The possible physiological and/or functional mechanisms responsible for callosal plasticity are discussed.     

On the origins of the conceptual system

Contrary to the conventional view of infancy as a sensorimotor period without conceptual thought, research over the past 20 years has shown that preverbal infants are capable of at least 3 conceptual functions: forming concepts with which to interpret the world, recall of the past, and engaging in conceptual generalization. Research is described indicating that the 1st concepts tend to be global in scope, such as animal or container, and that the course of conceptual development in the first 2 years is largely one of differentiating global concepts into more detailed concepts, such as dog or cup. A theory of how the 1st global concepts are formed from spatial information is briefly presented, including (a) a mechanism that redescribes spatial information into simpler but accessible form and (b) the primitives it uses for this purpose. Finally, the way concepts become more complex by means of language and analogical extension to nonspatial information is discussed.     

Beyond the family system

This paper comes from a workshop we ran at the 1980 A.F.T. Annual Conference at Bangor. It looks at the wider context of family therapy and the systemic view and attempts to open up areas for further investigation.     

Generalizing the Apple-Psych system

Each upgrade of computer hardware usually requires the development of new programming systems for psychological experimentation. Developing new software means learning a new system and unlearning an old one. To minimize this problem, a set of subroutine calls, derived from the Apple Psych system, can be implemented with different dialects of Pascal on different microcomputers.     

Deluding the motor system

How do we know that our own actions belong to us? How are we able to distinguish self-generated sensory events from those that arise externally? In this paper, I will briefly discuss experiments that were designed to investigate these questions. In particular, I will review psychophysical and neuroimaging studies that have investigated how we recognise the consequences of our own actions, and why patients with delusions of control confuse self-produced and externally produced actions and sensations. Studies investigating the failure of this 'self-monitoring' mechanism in patients with delusions of control will be discussed in the context of the hypothesis that overactivity in the parietal cortex and the cerebellum contribute to the misattribution of an action to an external source.     

Recalibration of the convergence system.

Adaptation to convergence-altering prism spectacles was studied. The subjects were trained for 8 min with either convergence-increasing or convergence-decreasing prisms. Before and after training they estimated the distance to a binocular dot varying in the stimulus it provided to convergence. Both the preadaptation and postadaptation estimates showed that the reciprocal of estimated target distance is linearly related to convergence. Further there was a consistent change in the direction of adaptation expected from the preadaptation to the postadaptation test. This change was accounted for in terms of a recalibration of the effective absolute convergence level.     

Coordination dynamics of the horse-rider system

The authors studied the interaction between rider and horse by measuring their ensemble motions in a trot sequence, comparing 1 expert and 1 novice rider. Whereas the novice's movements displayed transient departures from phase synchrony, the expert's motions were continuously phase-matched with those of the horse. The tight ensemble synchrony between the expert and the horse was accompanied by an increase in the temporal regularity of the oscillations of the trunk of the horse. Observed differences between expert and novice riders indicated that phase synchronization is by no means perfect but requires extended practice. Points of contact between horse and rider may haptically convey effective communication between them.     

The visual system of the cat

So much of our current knowledge about the neurophysiology of vision has come from studying the visual system of the cat. Using microelectrode techniques, neurophysiologists have examined in great detail the spatial properties of receptive fields of neurons at various levels of the feline nervous system, and headway is now being made in discovering the patterns of neural connections which give rise to the remarkable degree of stimulus selectivity characteristic of these neurons. This paper reviews the major findings concerning the visual system of the normal adult cat, from optics to visual cortex, and summarizes the physiological consequences of early visual deprivation on the visual nervous system of the cat. The review concludes with remarks about the validity of generalizing from cat neurophysiology to human vision.     

Neuroanatomy of the human affective system

We provide a brief overview of the structures associated with the limbic system using fixed human material. Although the review is by no means intended to be exhaustive, its purpose is to provide a tutorial on the primary structures that are involved in the experience, expression, and regulation of emotion and their anatomical location so that the reader can use this as a "pedagogical guide" for orientation and understanding of the many papers that appear in this Special Issue.     

Testing the limits of the phonetic mnemonic system

Three experiments tested the efficacy of the phonetic mnemonic system under varying conditions of application. The first study attempted unsuccessfully to replicate and extend the work of Morris and Greer (1984), who had shown training in the phonetic mnemonic method to facilitate memorization of a serial list of two-digit numbers. In the present study, subjects trained in the phonetic mnemonic method failed to learn lists of two-, four-, and six-digit numbers better than control subjects. The second experiment partially replicated the first, the differences being that training in the phonetic mnemonic method was strengthened, and time allotted for number recall was extended. Under these circumstances the phonetic mnemonic group recalled the two-, four-, and six-digit numbers significantly better than the control groups, a finding conforming with Morris and Greer's (1984) results. The third experiment partially replicated the second, everything being the same except that, in this case, subjects constructed their own key words representing each number, instead of these words being supplied by the experimenter. Under these conditions, subjects trained in the phonetic mnemonic method recalled significantly fewer numbers than control subjects.     

Indexing the approximate number system

Much recent research attention has focused on understanding individual differences in the approximate number system, a cognitive system believed to underlie human mathematical competence. To date researchers have used four main indices of ANS acuity, and have typically assumed that they measure similar properties. Here we report a study which questions this assumption. We demonstrate that the numerical ratio effect has poor test–retest reliability and that it does not relate to either Weber fractions or accuracy on nonsymbolic comparison tasks. Furthermore, we show that Weber fractions follow a strongly skewed distribution and that they have lower test–retest reliability than a simple accuracy measure. We conclude by arguing that in the future researchers interested in indexing individual differences in ANS acuity should use accuracy figures, not Weber fractions or numerical ratio effects.     

Interfacing for the SKED system

Four new interface modules, a new input module, a duration measuring module, an omnibus module, and a high-speed reader module, have been developed for the SKED interface to further optimize the use of the small computer in the laboratory.     

Measuring the approximate number system

Recent theories in numerical cognition propose the existence of an approximate number system (ANS) that supports the representation and processing of quantity information without symbols. It has been claimed that this system is present in infants, children, and adults, that it supports learning of symbolic mathematics, and that correctly harnessing the system during tuition will lead to educational benefits. Various experimental tasks have been used to investigate individuals' ANSs, and it has been assumed that these tasks measure the same system. We tested the relationship across six measures of the ANS. Surprisingly, despite typical performance on each task, adult participants' performances across the tasks were not correlated, and estimates of the acuity of individuals' ANSs from different tasks were unrelated. These results highlight methodological issues with tasks typically used to measure the ANS and call into question claims that individuals use a single system to complete all these tasks.     

Measuring the approximate number system

Recent theories in numerical cognition propose the existence of an approximate number system (ANS) that supports the representation and processing of quantity information without symbols. It has been claimed that this system is present in infants, children, and adults, that it supports learning of symbolic mathematics, and that correctly harnessing the system during tuition will lead to educational benefits. Various experimental tasks have been used to investigate individuals' ANSs, and it has been assumed that these tasks measure the same system. We tested the relationship across six measures of the ANS. Surprisingly, despite typical performance on each task, adult participants' performances across the tasks were not correlated, and estimates of the acuity of individuals' ANSs from different tasks were unrelated. These results highlight methodological issues with tasks typically used to measure the ANS and call into question claims that individuals use a single system to complete all these tasks.