Showing papers in "Human neurobiology in 1985"

Shifts in selective visual attention: towards the underlying neural circuitry.

Abstract: Psychophysical and physiological evidence indicates that the visual system of primates and humans has evolved a specialized processing focus moving across the visual scene. This study addresses the question of how simple networks of neuron-like elements can account for a variety of phenomena associated with this shift of selective visual attention. Specifically, we propose the following: (1) A number of elementary features, such as color, orientation, direction of movement, disparity etc. are represented in parallel in different topographical maps, called the early representation. (2) There exists a selective mapping from the early topographic representation into a more central non-topographic representation, such that at any instant the central representation contains the properties of only a single location in the visual scene, the selected location. We suggest that this mapping is the principal expression of early selective visual attention. One function of selective attention is to fuse information from different maps into one coherent whole. (3) Certain selection rules determine which locations will be mapped into the central representation. The major rule, using the conspicuity of locations in the early representation, is implemented using a so-called Winner-Take-All network. Inhibiting the selected location in this network causes an automatic shift towards the next most conspicious location. Additional rules are proximity and similarity preferences. We discuss how these rules can be implemented in neuron-like networks and suggest a possible role for the extensive back-projection from the visual cortex to the LGN.

"Memory of the future": an essay on the temporal organization of conscious awareness.

Abstract: The classical tripartite concept of time divided into past/present/future components, has been applied to the analysis of the functional cerebral substrate of conscious awareness. Attempts have been made to localize and to separate the neuronal machineries which are responsible for the experience of a past, a present, and a future. One's experience of a past is obviously related to one's memories. Memory mechanisms (in the conventional sense) have a well known functional relation to superficial and deep parts of the temporal lobe. Some such mechanisms presumably have a more widespread distribution. The experience of a present or a "Now-situation" is mediated by the sensory input. This input also exerts a role for conscious awareness of an inner Now-situation, independent of current afferent impulses, as shown by numerous observations on sensory deprivation. The main discussion is devoted to the experience of a future. Evidence is summarized that the frontal/prefrontal cortex handles the temporal organization of behaviour and cognition, and that the same structures house the action programs or plans for future behaviour and cognition. As these programs can be retained and recalled, they might be termed "memories of the future". It is suggested that they form the basis for anticipation and expectation as well as for the short and long-term planning of a goal-directed behavioural and cognitive repertoire. This repertoire for future use is based upon experiences of past events and the awareness of a Now-situation, and it is continuously rehearsed and optimized. Lesions or dysfunctions of the frontal/prefrontal cortex give rise to states characterized by a "loss of future", with consequent indifference, inactivity, lack of ambition, and inability to foresee the consequences of one's future behaviour. It is concluded that the prefrontal cortex is responsible for the temporal organization of behaviour and cognition due to its seemingly specific capacity to handle serial information and to extract causal relations from such information. Possibly the serial action programs which are stored in the prefrontal cortex are also used by the brain as templates for extracting meaningful (serial) information from the enormous, mainly non-serial, random, sensory noise to which the brain is constantly exposed. Without a "memory of the future" such an extraction cannot take place.

Frontal lobes and the temporal organization of memory.

Abstract: Evidence for a major involvement of the frontal cortex in various aspects of the temporal organization of memory has emerged from the study of patients who had sustained a unilateral frontal- or temporal-lobe excision for the control of cerebral seizures. It has now been established that the frontal cortex participates in judgements of the temporal order of recent events and of their frequency of occurrence, as well as in the planning and monitoring of the execution of self-determined sequences of responses. Some differential effects related to the side of the lesion were observed, these depending both on the nature of the stimulus material used and on the special demands of the task.

Motor control in humans with large-fiber sensory neuropathy.

Abstract: Upper limb motor control was evaluated in a series of patients with a large-fiber sensory neuropathy associated with impaired position, vibration and cutaneous sensation and absence of deep tendon reflexes. Muscular strength was normal or only minimally affected. In studies of wrist movement it was found that both postural maintenance and accuracy of wrist displacement were heavily dependent on visual guidance. Without vision the limb would drift in almost random directions, and during intended movements both the trajectory and movement end-point were abnormal. The defects in posture and voluntary movement control were reflected in the inability of patients to maintain consistent levels or emit consistent patterns of muscle activity. It is concluded that whereas central motor commands are sufficient to initiate movements proprioceptive afferent inputs are important for accurate postural maintenance and the fine control of movement.

The prefrontal cortex, mediator of cross-temporal contingencies.

Abstract: A large body of empirical evidence supports the notion of a critical role of the prefrontal cortex in the temporal organization of goal-directed behavioral sequences The key element of that role is the bridging of cross-temporal contingencies of behavior, in other words, the adjustment of the actions of the organism to temporally distant events and objectives By the analysis of lesion effects, neuroelectrical phenomena, and metabolic activity we are led to conclude that the prefrontal cortex subserves at least three cognitive functions that allow the mediation of cross-temporal contingencies and, thereby, the formation of temporally extended structures of behavior: short-term memory, preparatory set, and control of interference The three have a somewhat different topographic representation within the prefrontal cortex and thus the principle of its functional heterogeneity is upheld However, all three sustain the supraordinate role of the prefrontal cortex in the temporal integration of behavior

Effect of benzodiazepine hypnotics on all-night sleep EEG spectra.

Abstract: The effect of a single, oral bedtime dose of the benzodiazepine hypnotics flunitrazepam (FR; 2 mg), flurazepam (FR; 30 mg), and triazolam (TR; 05 mg) on the sleep stages and the sleep EEG was investigated in eight healthy, young subjects In comparison to the placebo night, all drugs reduced the percentage of stage 1 and REM sleep, increased stage 2, and decreased the number of stage shifts For FN and FR, some of these changes persisted in the postdrug night All-night spectral analysis of the EEG showed a reduction of low-frequency activity (025-100 Hz) in stages 2, 3 + 4 and REM sleep, changes that persisted for all three drugs in the post-drug night In the drug nights, activity in the spindle frequency range (11-14 Hz) was enhanced particularly in stage 2 and 3 + 4, activity in the high frequency range (17-25 Hz) particularly in REM sleep and stage 1 In the first third of the drug night, the depression of low-frequency activity in stage 2 was either absent (FR) or less prominent (FN, TR) than in the following part of the night The results demonstrate that benzodiazepine hypnotics induce specific changes in the EEG spectra which reflect the immediate and residual drug effects more sensitively than conventional sleep scores

Learning by statistical cooperation of self-interested neuron-like computing elements.

Abstract: Since the usual approaches to cooperative computation in networks of neuron-like computating elements do not assume that network components have any "preferences", they do not make substantive contact with game theoretic concepts, despite their use of some of the same terminology. In the approach presented here, however, each network component, or adaptive element, is a self-interested agent that prefers some inputs over others and "works" toward obtaining the most highly preferred inputs. Here we describe an adaptive element that is robust enough to learn to cooperate with other elements like itself in order to further its self-interests. It is argued that some of the longstanding problems concerning adaptation and learning by networks might be solvable by this form of cooperativity, and computer simulation experiments are described that show how networks of self-interested components that are sufficiently robust can solve rather difficult learning problems. We then place the approach in its proper historical and theoretical perspective through comparison with a number of related algorithms. A secondary aim of this article is to suggest that beyond what is explicitly illustrated here, there is a wealth of ideas from game theory and allied disciplines such as mathematical economics that can be of use in thinking about cooperative computation in both nervous systems and man-made systems.

Timing function of the frontal cortex in sequential motor and learning tasks.

Abstract: The timing aspects of human frontal lobe function are discussed in the light of the results of three experiments on movement-related cerebral potentials. Experiment I is based on use of a sequential tracking task and experiment II a motor learning task; experiment III deals with frontal hemispheric specialisation by comparing self-initiated writing and drawing. The Bereitschaftspotential (BP) preceding voluntary movement is maximum over the supplementary motor area (SMA) for all movements, including finger, toe, speech, and eye movements, regardless of each movement's different localisation in the brain, e.g., motor cortex, temporal lobe, or midbrain. The assumption that all motor events are governed by the primary (rolandic) motor cortex is erroneous. The motor system is widely decentralised. It is only when this decentralization is recognized that the close temporal association between the onset of all movements and the preceding Bereitschaftspotential in the SMA can be understood. A plausible explanation would be that the SMA decides on the starting time of all the various movements. The frontal function of motivation is not a single entity but has several subfunctions. It has to decide what to do, how to do and when to do. The latter is probably the task of the SMA. A comparison of different motivational situations makes this clear. In the usual BP paradigm, such as self-initiated simple finger or eye movements, only the SMA becomes active among all the frontal areas. If, however, motivation is required to modify motor programs in motor learning, as it is in experiment II, the entire convexity of the frontal lobe shows a large surface-negative potential, the amplitude of which reveals a significant positive correlation with the success in learning. On the other hand, in experiment I, which uses a manual pursuit-movement task requiring attention to unpredictable changes in stimulus direction but providing a fixed time for these changes (so that their timing is foreseeable), the SMA shows anticipatory behaviour; it takes the form of a large negative potential which ceases 0.5 s prior to the end of the directed-attention potential over parietooccipital areas. In other words, in this special situation, where the SMA can anticipate the onset of movement, it seems to delegate the final execution of the movement to the cortical area most specialised for it, in this case the parietooccipital cortex. The supervision of the tasks concerning what to do and how to do may be provided mainly by the orbital cortex and the frontolateral cortex, respectively (Kleist 1934).(ABSTRACT TRUNCATED AT 400 WORDS)

Schemas for the temporal organization of behaviour.

Abstract: Those aspects of the timing of behaviour are emphasized which derive from the need for the organism to coordinate its actions with objects in the environment. Such coordination may require the serial performance of certain actions, yet permit elements of concurrency as well. Perceptual and motor schemas are introduced as units for the functional description of behaviour intermediate between a purely phenomenological description and an account of the detailed neural mechanisms of behaviour. The language of coordinated control programs is outlined to suggest how such schemas are orchestrated in visually and tactilely guided behaviour. Finally, a crucial property of the timing of many movements is discussed: their division into a fast (feedforward, ballistic) phase followed by a slow (feedback) phase. This division is analyzed in the light of the effect of brain damage on reaching movements. Language: en

Cortical organization of voluntary behavior in man.

Abstract: The research on regional changes in metabolism and blood flow in the human cerebral cortex during physiological activations is reviewed, with special reference to the significance of these changes for the organization of voluntary behavior The only difference between cortical metabolic increases associated with voluntary behavior and cortical metabolic increases not associated with voluntary behavior was the activation of the primary motor cortex Prior to the execution of any specific brain work, the brain tuned and prepared the cortical fields that were expected to participate in the task This was reflected in metabolic increases in multiple cortical fields of a few cm2 which were then recruited for the task Execution of the task increased the metabolism in those same cortical fields The activated cortical fields constituted the largest functional elements of the cortex If voluntary behavior was required, fields in the motor areas were recruited; otherwise, the organization of voluntary behavior did not differ from other brain work In contrast to other cortical areas studied, the activation of the superior prefrontal cortex was independent on task-specific algorithms, sensory input and motor output Its anterior division was always activated in tasks that were carried out according to a prior instruction; the mid-division was activated when the brain fixed attention or switched it between different cortical fields; the posterior division was activated when the paradigm contained sequential contingencies The three sections of the superior prefrontal cortex participated in the organization of brain work by participating in the recruitment and attention control of cortical fields

Facial expressions of emotion in mother-infant interaction.

Abstract: Face movements of infants 2 months of age when they are interacting with their mothers give evidence both for innate representation of the mother as a partner in communication and for an emotional system that evaluates her expressions and regulates their interpersonal contact. Although the facial neuro-motor system is immature in infancy, it can generate many expressions that compare closely with those by which adults transmit emotions and control engagements and relationships. It also expresses rudiments of special motivation for speaking. Even newborns show clear evidence of organized facial expressions defining distinct communicative states that respond to maternal care. Emotional communication is multimodal; as infants gain in perceptuo-motor and cognitive powers, they both express and respond to simultaneous signals of affect in multiple channels of voice, gesture and postural change. Face expressions form but part of a stream of motor evidence of central affective state and its changes. Mothers present to infants a form of expressive activity (baby talk) that has clearly marked synchronous visible and audible features. The precocious expressive capacities and sensitivities of infants and maternal fostering of them would appear to be a human adaptation to facilitate development of observational learning and language. Developments in the first year expand the scope of communication and play without changing the fundamental emotional code by which infant and familiar caretakers construct and defend their special relationships.

On the perception of time during prolonged temporal isolation.

Abstract: UNLABELLED In an underground isolation unit, 42 subjects were living singly for time spans of at least 7 days up to more than a month. Except three who were entrained to 24 h by an externally controlled light-dark cycle (LD), subjects had no time cues and developed free-running circadian rhythms either in self-selected LD-cycles or in constant illumination. Each subject had to give a signal whenever he thought that 1 h had passed. In addition, 30 subjects produced short-time intervals within the range from 10 to 120 s. RESULTS The 1-h estimates were longer than 1 h, and had a strong positive correlation with the duration of wakefulness alpha as well as with the length of the circadian cycle. The short time estimates were equally distributed between under- and over-estimation of the required interval, and they were neither correlated with the 1-h estimates nor with alpha. It is concluded that long and short time estimates are based on different mechanisms.

Temporal tracking and synchronization strategies.

Abstract: Timing measures were obtained from subjects instructed to tap a Morse key in synchrony with a metronome which marked a timing pattern consisting of alternating blocks of intervals of imperceptibly different duration. "Synchronization strategies", which consisted of computer-simulated sets of rules, or algorithms, hypothesized to be the basis of synchronization behavior, were used to simulate tapping sequences in response to the same metronome sequences. The human and computer-simulated synchronization data were analyzed identically and compared to determine which of the postulated strategies could explain the observed human tapping behavior. The strategies generating timing data statistically indistinguishable from the human data involve a pattern of human-metronome interaction, and a corresponding transfer of information, more complex and subtle than previous investigations had implied.

Dopaminergic drugs improve human visual contrast sensitivity.

Abstract: Effects of dopaminergic drugs (L-dopa plus benserazide, or nomifensine) on human visual function have been tested in healthy volunteers by measuring the psychophysical contrast sensitivity for sinusoidal gratings of various spatial frequencies. After drug administration the contrast sensitivity improved in all subjects over a limited range of medium to high spatial frequencies.

Napping behavior during "spontaneous internal desynchronization": sleep remains in synchrony with body temperature.

Abstract: Patterns of sleep and wakefulness exhibited in an environment without time cues are generally considered to be monophasic, with a distinct relationship between sleep episodes and the minimum of body core temperature. In some cases this relationship between major sleep episodes and temperature becomes replaced by an apparently varying phase relationship between the two variables called "spontaneous internal desynchronization". In the present study the sleep-wake and temperature data of six subjects living in an environment without time cues and exhibiting internal desynchronization were reanalyzed to include subjectively designated naps. Two groups of naps were identified based on their phase positions relative to temperature, with one group occurring around the temperature minimum and another group clustering approximately halfway between successive minima. The results support the suggestion that neither monophasic sleep placement nor sleep patterns typically associated with spontaneous internal desynchronization reflect biological sleep tendency. Rather, sleep tendency is reflected more accurately by the bimodal sleep patterns exhibited by subjects who are allowed to time their sleep and waking with no restrictions.

Failure to confirm a correlation between electromyogram and final position.

Abstract: Attempts were made to correlate angular position of the elbow with integrated electromyographic activity of biceps and triceps. Five conditions were studied: isometric co-contraction and immediately after fast flexion, slow flexion, fast extension and slow extension movements. Neither activity of biceps, activity of triceps or the ratio of activities correlated with any of four different angles for these five conditions.

Human contrast sensitivity: regional retinal differences.

Abstract: Contrast sensitivity functions of foveal and of perifoveal upper and lower hemiretinal regions were measured in a population of twenty subjects. Foveal stimuli yielded consistently higher contrast sensitivities as well as a shift of the maximal sensitivity towards higher spatial frequencies as compared to perifoveal stimuli. The upper hemiretinal area was more sensitive at all spatial frequencies tested than the corresponding lower hemiretinal area. The statistical comparisons were highly significant, indicating not only regional retinal differences in visual acuity as reflected by the different contrast threshold levels at the highest spatial frequency, but also global differences between the upper and lower hemiretina systems not restricted to certain spatial frequency channels.

Time, space and value.

Abstract: The ability of animals to associate stimuli depends on whether the stimuli are processed by the cognitive system or the affective system. Historically, a distinction was made between "thinking" and "feeling" by the empirical philosophers of the Renaissance. Recent evidence indicates that cognition and affect can be fruitfully applied to animal research. When animals are required to search an external environment for hidden food baits, they display an objective mastery of time and space as if they have acquired a "cognitive map" of the test area. Tests of an animal's ability to span the time between two external events yield intervals which can best be measured in seconds or fractions thereof. When animals consume a food, the affective value of that food is adjusted according to its utility in the internal milieu. If the food is nutritious, visceral feedback raises the preference value of the food. If nausea ensues, the taste becomes disgusting. Tests of an animal's ability to span the time between eating and nausea yield intervals which can best be described in hours or fractions thereof. Cognitive and affective processes are qualitatively distinct and subserved by different neural systems, yet they are both essential for associative learning. We offer a theoretical scheme designed to weld the two components into a single unitary sequence.

Hemispheric asymmetry in face perception tasks of different cognitive requirement.

Abstract: Three laterality experiments using tasks of different cognitive requirement were performed in order to determine the stage at which hemispheric differences in face perception arise. All experiments employed the same set of faces and a vocal reaction time paradigm. In experiment 1, subjects were required to discriminate male from female faces and no hemispheric asymmetries were found. In experiment 2, subjects were required to decide whether or not faces were of famous or unknown people and a right hemisphere advantage was found. Finally, in experiment 3 subjects were required to verbally identify the famous faces and no hemispheric differences were found. The results suggest that a right hemisphere superiority exists for the comparison of stimulus faces with an internal representation. Contrary to expectation, face naming does not result in a selective left hemisphere involvement.

Hidden-face recognition: comparing foveal and extrafoveal performance.

Abstract: Ambiguous stimulus material was computer-generated by superimposing image components of a target-face and either a random checkerboard texture or a masking face. The recognition of the target-face was studied both for foveal and extrafoveal vision. Compensation of the peripheral disadvantage in image discrimination by rescaling the stimulus size was possible only in the case of texture. Comparable results were obtained from combining band-pass image components of the portraits. Results suggest that it is the relative inability to recover a signal from spatially correlated noise that characterizes visual discrimination in the peripheral visual field.

Left hemispheric functional compensation in prosopagnosia? A tachistoscopic study with unilaterally lesioned patients.

Abstract: Clinical observations suggest left hemispheric compensation for prosopagnosia in patients with isolated right posterior lesions. To test this hypothesis we investigated six patients with right posterior lesions, three with and three without prosopagnosia, with a series of tachistoscopic matching experiments. Faces with and without paraphernalia, shapes, objects and words were presented at different exposure durations (unlimited, 1000, 200, 50 and 20 ms). Prosopagnosia patients performed better than non-prosopagnosia patients if pure faces (eyes, nose and mouth only) were presented for an unlimited time, but performed worse than non-prosopagnosia patients if exposure duration was reduced. Patients with prosopagnosia were especially handicapped when required to match emotional expressions. Both patient groups had no difficulty in matching objects and words, even at short exposure durations. The results are discussed with respect to a possible left hemispheric compensation in prosopagnosia patients.

Brain theory and cooperative computation.

Abstract: "Top-down" brain theory, based upon functional analysis of cognitive processes in terms of interacting schemas, is distinguished from "bottom-up" brain theory based on analysis of the dynamics of neural nets. "Cooperative computation" is proposed as the style of interaction of neural subsystems at various levels. Perceptual schemas are introduced as the building blocks for the representation of the perceived environment, and motor schemas serve as control systems to be coordinated into programs for the control of movement. A cooperative computation view of the design of machine vision systems is exemplified both by an algorithm for computing optic flow which offers interesting insights into the evolution of hierarchical neural structures, and by an analysis of knowledge representation for machine interpretation of visual scenes. The interaction between top-down analysis and detailed neural modelling is illustrated by the study of visuomotor coordination in frogs and toads.

Insulin-like immunoreactivity in human cerebrospinal-fluid is independent of insulin blood levels.

Abstract: Samples of cerebrospinal fluid were taken from 81 patients and investigated for insulin-like immunoreactivity by use of radioimmunoassay. The data suggest that IRI levels of Liquor cerebrospinalis are independent of blood insulin concentrations. It is supposed that nervous tissue is the source of IRI in the cerebrospinal fluid.

A developmental study of face recognition in children and adolescents.

Abstract: A slide projection test was applied to investigate the ability of children to recognize faces and vases. Boys and girls between age 7 and 16 years were investigated. During the inspection series the subjects had to judge 42 black and white photographs of 14 male faces, 14 female faces and 14 vases. One hour after the inspection series a two-choice recognition test (6-s presentation) was performed and 1 week later the second recognition test. (1) During the inspection series the subjects had to make 42 forced-choice decisions as to whether they liked or disliked the projected face or vase. The number of positive responses for vases was in all age groups significantly higher than for faces. For both items positive response scores decreased with age. (2) In all age groups recognition and recall after 1 h was better for faces than for vases. For both items the 7- and 8-year-old children had a significantly higher error score than the other age groups. Boys reached adult performance levels at 9-10 years of age. Under age 15 to 16 years, male subjects had a significantly better face recognition ability than female subjects. This is in contrast to the repeatedly found adult female superiority in face recognition. The sex of the faces and the emotional responses during the inspection series were found to have a slight influence on face recognition. (3) Correct item recognition decreased after 1 week for those items (faces and vases) seen in the inspection series only and not in the first test after 1 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Eye movements in relation to loss and regaining of fusion of disjunctively moving random-dot stereograms.

Abstract: Horizontal eye movements of four subjects were recorded with a scleral induction-coil technique during dichoptic viewing of a random-dot stereogram. The stereogram contained two depth planes. The two half-images of the stereogram were slowly moved in opposite lateral directions beyond the limit of divergence; subsequently the movements of both images were reversed. Ocular vergence followed image vergence of the foveally viewed part of the stereogram during fusion. Binocular disparity increased beyond a certain angle of divergence. Before loss and after regain of fusion the same relation was found between binocular disparity and angle of divergence. The size of binocular disparity that did evoke vergence responses was limited to about 4 deg arc; this range was larger than the maximum amount of binocular disparity (1 to 2 deg arc) that could be fused. Shifts in fixation from the one depth plane to the other one were executed by rapid vergence movements. These vergence movements were slower than saccades but still exceeded the maximal velocities generally assumed for vergence.

The percentage of projection neurons and interneurons in the human lateral geniculate nucleus.

Abstract: Projection neurons and local circuit neurons of the human lateral geniculate nucleus (LGN) offer different patterns of lipofuscin pigmentation. One type of projection cell (type I neuron) and two varieties of local circuit neurons (type II and type III neurons) can be distinguished on account of their characteristic pigmentation. The majority of the nerve cells are type I projection neurons. Pigmented type II neurons comprise about 8.5% and type III neurons devoid of pigment amount to only 0.2% of the nerve cells.

Trigger activation of the paradoxical salivatory response to atropine in the parasympathetically denervated human parotid gland.

Abstract: The author describes a specific intermediate condition of the response to atropine during the 2nd stage of denervation of the human parotid gland. Of the entire cohort of 110 subjects, some 20 subjects have been observed systematically. They demonstrated an extremely intense atropine salivation that followed an additional trigger activation, namely food or acid irritation of the mouth mucosa. The initial phase of such a stimulation was characterized by a sharp, explosive increase in secretion. The following conclusions have been inferred: (1) in the 2nd stage of parasympathetic denervation of the human parotid gland, there emerges a specific intermediate condition of 'readiness' for an extremely intense paradoxical salivatory response to atropine and other cholinolytics; (2) the pre-start 'readiness' state may be activated by means of adding a trigger signal followed by an explosive occurrence of abundant secretion; (3) only food or acid irritation, even to a minimal extent, of the mouth cavity may serve a specific trigger signal; (4) a stable state of this trigger readiness has been observed in 20 subjects for years, while in other subjects it has been observed as a transitory event between the 1st and the 3rd stages of denervation and during the regression of symptoms in the rehabilitation period; (5) suggestions have been made concerning the trigger activation mechanism of the atropine salivatory paradox and the evolutionary, model and clinical significance of the events described.

Comments on time in action and perception.

Abstract: Time as a physiological sequence of connected states differs in some respects from the legion of processes in nature that proceed in the temporal dimension. Within the living organism it is intimately joined to the unknown mechanism of memory in both its longand short-time versions. The beginning and the end of a short-time sequence are held together by short-time memory. A striking example of the role of long-time memory is Wilder Penfield's well-known finding while stimulating the temporal lobe of a patient. She responded by recalling a long lost happening in great detail, as it had developed, in a sequence of perfect temporal precision. The patient re-experiencing the event was at the same time aware of lying on the hospital operating table. This, by the way, elicited Sherrington's comment that it must be nice to hear the preparation speak! Numerous well-timed sequences are known to physiologists as belonging to the genetic make-up; for instance, reflex deglutition which engages l2 muscles on either side in a well-regulated succession (Doty 1968). Others are acquired, like the majority of programmed motor acts, some of which need a very high degree of accuracy in the timing of the muscles cooperating in a movement. A component of adaptation enters into this process because of the limiting conditions set by the progressive changes of the inertia and momentum of the moving parts with age. Walking and running