Perceptual categorization is associated with sensory performance in patients with unilateral cerebral lesions.

In this investigation of perceptual categorization (PC), .right-sided brain-damaged patients (RBD) were not impaired for PC of line drawings of animals relative to left-sided brain-damaged (LBD) patients, contrary to what was expected from previous work. Moreover, in both LBD and RBD patients PC performance was significantly associated with performance on a series of 6 sensory tests. These differed from conventional tests in that successive comparisons were required; and in 2 of the 6 tests gratings were discriminated.

Impaired visual perceptual categorization in right brain-damaged patients: failure to replicate.

The association of both Perceptual Categorization (PC) and Semantic Categorization (SC) with sensory performance was investigated. 28 RBD, 27 LBD and 21 non-brain-damaged subjects were tested with the PC and SC tasks described by Warrington and Taylor (1978) and with 6 sensory tasks. PC was related to sensory performance in RBD but not in LBD patients. SC was only marginally associated with sensory ability in both lesion groups. RBD and LBD patients differed significantly at neither PC nor at SC. Thus the dissociation between PC and SC, described by Warrington and Taylor (1978) was not replicated. Moreover, PC and SC were significantly correlated in both RBD and LBD patients. This suggests that the serial organization of PC and SC is questionable. It is concluded that the associations we obtained between SC, PC and sensory performance are likely to be functional. The contribution of a cognitive factor ("abstraction") to PC and SC is discussed.

Cross-modal performance: behavioural processes, phylogenetic considerations and neural mechanisms.

Issues relating to cross-modal performance (CMP) are examined from various points of view, with major emphasis on phylogenetic comparisons and neurological mechanisms. Although it now seems likely that certain distinctions that were made based on training procedures (i.e., among transfer, matching, and recognition) have no functional significance, research on this topic has demonstrated how the level of performance is affected by certain task variables (such as number of trials in the first modality). It has not yet been shown that these relationships differ from ones that would be seen in comparable within-modal studies. Overall phylogenetic differences specific to CMP cannot be sustained from the data for humans, apes, monkeys, and non-primates. However, two possible differences--one phylogenetic and one ontogenetic--require further study. Metaphorical matching has not been demonstrated in nonhumans, and it may be the case that 'categorical' CMP appears earlier in development than 'specific' CMP. Efforts to establish that CMP is mediated by representations localized in regions of polysensory neural convergence have not provided convincing evidence, so that 'leakage' between perceptual/memory systems previously considered to be modality-specific is proposed as the mechanism for CMP. Based primarily upon findings from a study using 2-DG, the suggestion is made that one pathway for such leakage is through the ventral claustrum. Polysensory areas of cortex may play a special role during the initial formation of a multisensory engram.

"Object vision" and "spatial vision": the neuropsychological evidence for the distinction.

The distinction between "object vision" and "spatial vision" was made by Ungerleider and Mishkin (1982) on the evidence of behavioural and neuroanatomical studies, largely with monkeys. It holds that separate cortical systems are involved, the occipito-temporal in object vision, the occipito-parietal in spatial vision. This distinction has been unquestioned; it appears as though fact in influential textbooks; but has never been subjected to critical scrutiny. Theoretically, there are substantial difficulties, for instance because during perception objects do not form a special category, apart from their features; and because shape, pattern and size are spatial features of objects. Empirically, for the monkey the behavioural distinction does not hold (because parietal cortex is not the sole cortical area involved in "spatial vision"); and in man because parietal lesions have long been known to lead to impaired perception of incomplete pictures. Moreover, although Ungerleider and Mishkin do not generalise their distinction to touch, this sense deserves consideration, given that Mishkin had earlier argued that vision and touch have a similar organisation. In touch there are direct anatomical connections between the areas serving "object touch" and "spatial touch", and both in man and in the monkey it seems established that the same region processes spatial performance in vision and in touch. Further work is needed particularly on the spatial disorder after parietal lesions: in the monkey, research has frequently been confined to one non-specific test; in man, important differences related to the laterality of the lesion, have only recently emerged. Then "spatial performance" may be found to be more closely linked to motor output than to sensory input.

The development of independent foci in epileptic patients.

The electroencephalograms of 309 unselected epileptic patients were reexamined to ascertain the incidence of independent secondary discharges. In 41 patients (13%), a simple one-sided focus, without evidence of independent secondary discharges, was found (group 1); in 33 patients (11%), an epileptic focus with certain evidence of independent secondary discharges was found (group 2). These two groups were compared with respect to multiple variables (eg, seizure type, time course of the epileptic illness, site of foci, medication, neurological status), and significant differences between the two groups were obtained (eg, with respect to frequency of seizures, duration of seizures, number of anticonvulsive drugs being taken, and in other respects). Our findings are compared with earlier work, and it is concluded that they do not support the conventional models of secondary epileptogenesis.

The neural structures involved in cross-modal recognition and tactile discrimination performance: an investigation using 2-DG.

Given the failure of the ablation method to identify the neural structures/systems that are crucial for cross-modal recognition (CMR) and for tactile discrimination performance (TDP), we injected radioactive 2-deoxy-[14C]glucose (2-DG) into monkeys trained to a high level of CMR or TDP. Nine monkeys were trained to recognize in one sense-modality, to a level greater than 80% correct, the objects experienced in the alternate modality on only a single prior trial. After injection, CMR was continued (Expt. 1a) exactly as before, except that all CMR problems were now in only one direction; or (Expt. 1b) the second--the CMR--trial of each problem was not realized (i.e. no objects were available in the second modality) so that the monkey merely 'expected' the cross-modal trial. Nine other monkeys were trained on a graded roughness discrimination task with conventional 'titration' procedures to a stable level of performance, either (Expt. 2a) without having undergone any cortical removal, or (Expt. 2b) after unilateral removal--contralateral or ipsilateral to the preferred hand--of the posterior insula or of the second somatosensory projection cortex (SII). Exactly the same training procedures were continued in Expt. 2 after injection of 2-DG. Coronal radiographs were made at 490 microns for all 18 monkeys (and also for a 19th, which served as a control in Expt. 1b). The optical densities of the autoradiographs were measured quantitatively in respect of 50 structures or part-structures (e.g. sulci, thalamic nuclei, subcortical structures); they were rated either with the aid of 'pseudo-colours' produced by the computer, or directly by judging the black/white optical densities, in respect of 29 other structures. These 79 structures were then the dependent variables in MANOVAs or ANOVAs, to determine differences between groups; or within groups with respect to the left/right and ipsilateral/contralateral hemispheres; or interaction effects. It was found that certain structures (e.g. the ventral portion of the claustrum, the insula with its extension ventrally into the fundus, nucleus Medialis dorsalis and nucleus Pulvinar oralis) repeatedly, whereas others (e.g. the amygdala) never gave rise to significant outcomes. Structures in the left cerebral hemisphere were frequently found to be more strongly labelled than those in the right hemisphere.(ABSTRACT TRUNCATED AT 400 WORDS)

Aimed movements to visual targets in hemiplegic and normal children: is the "good" hand of children with infantile hemiplegia also normal?

The accuracy, reaction and movement time of pointing movements to visual targets were examined in children aged 3-13 yr with infantile hemiplegia and compared to those of comparably aged normal children. Hemiplegic children pointed with the "good" hand (i.e. ipsilateral to the lesion). Half the normal children used the preferred hand, half the non-preferred hand. Movements were made with unrestricted/restricted visual feedback, when movement distance was short/medium/long, and when number of target alternatives were 2/4/8. Normal children using the preferred hand were more accurate but reacted more slowly than children using the non-preferred hand. The performance of most of the hemiplegic children with bilateral and/or unilateral lesions was impaired; degree of accuracy was related to the extent of the brain lesion; and reaction time was related to the level of intelligence. It was concluded that unilateral lesions in children can result in bilateral visuomotor impairment.

Guidance of visual reaching with the aid of a TV monitor: the effects of monitor position and of left/right and up/down reversals of the image in relation to age.

Children, aged 2-9 years, were seated alongside a wall containing an opening through which they could reach with their preferred hand. Targets ("ink blots"), which could not be felt, were attached to the other (rear) side of the wall, around the opening. The child could see directly neither the target nor its hand beyond the front side of the wall; but both were visible on a TV monitor. The image on the screen of the monitor originated from a camera viewing the rear (target) side of the wall at the level of the central opening. The monitor screen was either (a) parallel to the wall, but rotated 180 degrees with respect to the axis of the camera, i.e. facing the camera; or (b) at 90 degrees to the wall; or (c) in a position similar to (a) but visible in a mirror attached to the front side of the wall and therefore in effect "aligned" with the axis of the camera. The image the child saw was either (1) electronically unswitched, i.e. when the target was towards the east on the wall it was to the west on the monitor in monitor position (a), or to the north in position (b), or to the "east" in position (c); or (2) left/right reversed relative to (1); or (3) up/down reversed relative to (1); or (4) both left/right and up/down reversed. The dependent variable was the time taken for the child to place the palm of the hand over the target (time was measured to 0.1 sec on video-recorder with a superimposed time display). Position of the monitor, comparing conditions (a)-(c), gave only minor, perhaps age-related, effects. Left/right reversals were easier than up/down reversals under monitor positions (a) and (b), but not under (c); but both reversals could be achieved by age 3 or older; hardest was condition (4). However, with monitor positions (a) and (b) children, at all ages we tested, found condition (1) ("east gives west/north") easier than (2) ("east gives east/south"), whereas for adults these conditions were equally easy, or they found (2) easier than (1); but with monitor position (c) condition (1), now "east gives east", was easiest. Moreover, the claim that chimpanzees but not monkeys can achieve accurate reaching under the conditions varied in this study seems premature: the chimpanzees may have made use of strategies based on uncontrolled cues.

Hand preference, ability, and hemispheric specialization: in how far are these factors related in the monkey?

Reasons are given for preferring the term "hand-ability" to "hand-preference", especially in animals, for discussions of HS. Different kinds of HS are described for man and for the monkey, with emphasis on the importance of the precise task to be performed for the determination of HS ("act-specific HS"). Exceptional kinds of HS in the monkey are reported.

The relationship between metaphoric and crossmodal abilities during development.

Metaphoric and crossmodal abilities were investigated in children, aged 3-8 years. For this study metaphoric performance was regarded as based on the production of a relationship between physically dissimilar stimuli (presented in two sense-modalities), which are not normally perceived as being related. It was asked at what age crossmodal performance, based on specific rather than global/categorical differences within stimulus pairs, can be regarded as distinct from metaphoric performance. In Expt. 1, metaphoric and crossmodal two-trial "recognition" tasks were given in Touch and Vision at all ages. In Expt. 2,3- and 4-year-olds were first trained over 6-20 trials to choose one of two stimuli in one modality (Touch or Vision) and then given one "recognition" trial in the alternate modality. Children as young as three could relate specific physical stimulus differences across sense-modalities. Although metaphoric recognition was present on two problems in children aged 3 and 4 years, metaphoric performance was inferior to crossmodal performance at all ages. Crossmodal abilities improved with age due to improved intramodal skills; such intramodal improvement can probably account for only a part of the improvement on the metaphoric task. Reasons are given why metaphoric and crossmodal abilities may be separate over the age range 3-8 years.

Tactile recognition of mirror images by children: intermanual transfer and rotation of the palm.

In order to evaluate the importance of the axis of stimulus presentation, inter- and intramanual recognition of mirror pairs was studied with the stimulus materials aligned along the front/back axis (whereas in previous work the mirror pairs were aligned along the left/right axis). Children were allowed to feel shapes with the whole hand, with only four fingers (excluding the thumb), or with only the index finger. After learning with one hand, recognition was tested in experiment 1 with the other hand; after learning with one orientation of the hand (palm down or up), recognition was tested in experiment 2 with the other orientation (palm up or down) of the same hand; after learning with one coronal alignment of the hand (to the left or right), recognition was tested in experiment 3 with the other alignment (to the right or left), but without rotation, of the same hand. Significantly fewer intermanual recognition errors were made on mirror pairs with the materials oriented along the front/back axis than in previous work when oriented along the left/right axis. This supports the suggestion that such errors arise when the stimuli are oriented along the left/right axis during formation of the memory trace. The same trend was unexpectedly obtained for intramanual recognition errors (after rotation of the hand). These errors (after hand rotation) are largely due to coding with respect to the hand; they are reduced when the hand is not aligned with the body axis, since then coding can also occur in relation to the environment.

Unilateral removal of the posterior insula or of area SII: inconsistent effects on tactile, visual and auditory performance in the monkey.

Unilateral removals of the posterior insula or of the second somatic sensory projection area (SII) were made in respectively 8 and 6 monkeys. These animals were divided into a 'contralateral' group of 7 with removals from the hemisphere opposite to the preferred hand; and an 'ipsilateral' group of 7 animals with removals from the hemisphere on the same side as the preferred hand. In addition, 6 unoperated monkeys were trained comparably. Both the contralateral and ipsilateral animals were impaired in comparison with unoperated animals at threshold discriminations of graded roughness and/or sizes when using the hand opposite the removals. Animals with contralateral ablations were impaired in comparison with those having ipsilateral ablations only in a few of many instances: with the hand ipsilateral to the removals at re-learning a tactile discrimination and at learning an auditory discrimination; with the hand opposite to the removals when it was initially used on visual or auditory tasks that had already been mastered with the other hand. It is suggested that in addition to SII the insula is also organized asymmetrically in relation to hand preference in the monkey, but the insula of the predominant hemisphere may be involved as much in non-tactual as tactual performances, for example in tasks involving successive discrimination and when a familiar task has to be performed initially with the other hand.

Differential accuracy of aimed movements to visual and somatic targets in young children.

Children, aged 2.5-8 years, were required to touch accurately a target located either on their bodies or on the chair in which they sat. Movements were made when visual information was: 1. complete (target lit for 3 s, room illuminated); 2. partial (target lit for 3 s, room dark); 3. reduced (target lit for 0.7 s, room dark); and finally, when the target was somatically specified. Movements to visible targets did not differ in any important way as a function of target location with respect to on/off body. Accuracy improved with age to visually but noto somatically specified targets, decreased with decreasing availability of visual information, and was poorest to somatically specified targets. We conclude that during development, the sense-modality through which the target is specified and the visibility of the arm/hand during the movement, but not the personal/extra personal visible space in which the target is located, are important determinants of reaching performance.

Cross-modal recognition of familiar and unfamiliar objects by the monkey: the effects of ablation of polysensory neocortex or of the amygdaloid complex.

Nine rhesus monkeys were trained to a standard level of cross-modal recognition (CMR) in the directions vision to touch and touch to vision. Their level of performance remained essentially unchanged with unfamiliar objects. Five then received bilateral removals of frontal, temporal and parietal polysensory cortex in one stage or successively, and 4 underwent removal of the amygdaloid complex in one stage. All animals were retrained to criterion with familiar objects and then again tested with unfamiliar objects. Postoperatively, the monkeys with extensive neocortical removals were unimpaired or slightly impaired with familiar objects, and slightly impaired (in only one direction) with unfamiliar objects. The animals with amygdaloid ablations showed a different pattern of change: with familiar objects they were unimpaired (if removals were less extensive), or were severely but transiently impaired (if the removals of the amygdala were more extensive and/or other structures were involved); with unfamiliar objects they were unimpaired, tending to improve. The neocortical polysensory areas may be necessary for generating new visual representations during learning--a performance required only for the CMR of unfamiliar objects.

The accuracy of aimed movements to visual targets during development: the role of visual information.

Children aged 1.5 to 8 years were required to touch accurately an illuminated target lamp located on a vertical board. Movements were made when visual information was complete (target lit for 3 s, room illuminated; partial (target lit for 3 s, room dark, and reduced (target lit for 0.7 s, room dark). Dependent variables were response accuracy, reaction time, and movement time. Accuracy decreased with decreasing availability of visual information and improved with age under all conditions. Reaction times were shorter in the dark (Conditions 2 and 3) than in the light; they decreased with age up to age 5 and did not continue to decrease thereafter. Movement time did not change with age under Conditions 1 and 3 but tended to increase with age under Condition 2. Slower movements were more accurate at all ages, provided visual feedback could be utilized. Increased reliance on the strategy "slower movements yield higher accuracy" was held to account for developmental changes under Condition 2, whereas in Conditions 1 and 3 improvement in the efficiency of motor preprogramming was implicated.

Cross-modal recognition by the monkey: can the experience in the first modality be reduced to a single trial?

Using the cross-modal recognition procedure previously described, but now progressively reducing the number of learning trials given in the first sense modality, three unselected and unoperated rhesus monkeys (and one with bilateral removals of frontal, temporal and parietal polysensory cortex) were able to maintain an average level of 75% correct cross-modal recognition with only 1-3 learning trials. The pool size seemed less important than the familiarity of the objects. No discontinuity between single-trial and multiple-trial learning procedures was detected. Instead, the number of objects available at one time during learning was regarded as critical for distinguishing between these two kinds of learning procedure.

Tactile recognition of laterally inverted mirror images by children: intermanual transfer and rotation of the palm.

Intermanual tactile recognition of laterally inverted mirror shapes was studied, with special reference to the role of the thumb. Children were allowed to feel the shapes either with the whole hand, with only four fingers (excluding the thumb), or with only the index finger. Intramanual recognition was also studied after rotation of the hand from the palm down/up to the palm up/down orientation. The thumb was found not to be important for intermanual mirror reversals, and only of limited importance for intramanual reversals. There was no evidence that coding with reference to the hand is of importance for either inter or intramamual reversals. The explanations for the two kinds of reversals are quite different.

Unilateral spatial neglect and defective performance in one half of space.

The performance of 80 unselected patients with unilateral cerebral lesions (verified by CT scan) was compared with that of 34 control subjects on 6 "screening" tests for visual, auditory, tactile, kinaesthetic, motor and conceptual neglect. The performance of all 114 patients was tested comparably on the left and right sides, and (except for motor neglect) also centrally. Cut-off scores were determined so that performance inferior to 95% of the control range could be identified. The criterion for neglect was contralateral defect in the absence of ipsilateral and of central defect. With this procedure 30 patients were identified as showing neglect (5 visual, 6 auditory, 5 tactile and 4 motor--all 20 patients showing only one form of neglect; 10 with various combinations of neglect). In 27 of these 30 patients the lesion was found to be right-sided. The performance of various groups of patients with neglect was then compared with that of the 50 patients without neglect on 26 "evaluative" tests, designed to characterize the different varieties of neglect. For this comparison discriminant analysis was used. The outcome of two discriminant analyses instance a patient with visual and auditory neglect is not similar to a patient either with exclusively visual or with exclusively auditory neglect; (2) mixed, tactile and motor neglect are easy to discriminate from other kinds of neglect, whereas visual and auditory neglect are less easy to discriminate, particularly from patients without neglect; (3) the discriminant functions seem to reflect general spatial defect not confined to one side of space; differential spatial performance to the contralateral/ipsilateral sides; and manipulation. The findings are discussed in relation to previous interpretations of neglect; the defect is regarded as one of local attention.

Confusion of laterally inverted mirror-images: a relationship to brain anatomy?

Whereas in the monkey brain the representation of spatial direction (left/ right) is the same for visual and for tactual inflow, in the human brain visual and tactual lateral directions are not aligned with respect to one another. This anatomical feature of the human brain may account in part for the particular difficulty young sighted children have with laterally inverted forms. A small group of children who were totally blind since birth distinguished mirror pairs by touch significantly more easily than did sighted children of comparable age; and monkeys succeeded at cross-modal recognition of laterally inverted mirror pairs better (relative to control pairs) than did sighted children.

Cognitive development in epilepsy. The relative influence of epileptic activity and of brain damage.

A total of 37 children, aged between 12 and 18 years and resident in an epileptic colony, were assessed in several ways for the frequency of their epileptic discharging activity and for the extent of underlying brain pathology. In addition, the children were evaluated for their level of performance on various tests of cognitive and visuo-motor functions. The influence on test performance of the discharging activity and of the extent of pathology was then compared, taking other factors such as age at onset of the seizures, duration of the epileptic illness and level of medication into account as far as possible. Only two factors, namely certain indices of discharging activity and level of medication, were found to have significantly influenced particular aspects of cognitive performance; it was impossible to document an influence of brain pathology statistically.