Louis D. Costa

Orienting and habituation to auditory stimuli: A study of short terms changes in average evoked responses ☆

Abstract Short term habituation in human subjects was studied by a method which provided a stimulus by stimulus analysis of averaged evoked responses. Tones delivered every 2 sec resulted in a rapid drop, during the first few stimuli, in the amplitude of the positive component of vertex responses which peaks between 150 and 200 msec; but no similar change was found for tones delivered every 10 sec. The rapid drop for the faster rate of stimulation was considered to have only the appearance of habituation, and was viewed as reflecting refractoriness within the auditory system. On the other hand, when the first stimulus was presented in an unpredictable manner it elicited a large positive component with a peak latency of about 300 msec. Similar responses were obtained when an unpredictable pitch change was presented in an effort to elicit dishabituation. Predictable pitch changes did not produce these results. The 300 msec component was seen as reflecting a shift of attention associated with the orienting response.

Topography of the human motor potential

Abstract The motor potential (MP) accompanying voluntary movements is maximal over Rolandic cortex and shows a somatotopic distribution for contractions of various muscles similar to that obtained by cortical stimulation. The MP field distribution was shown to be compatible with its generation by a source of comparable size to the excitable motor cortex. The late component of the somato-sensory evoked response (SER) elicited by peripheral nerve stimulation had a similar distribution, but extended slightly posterior to that of the MP. These differences in distribution between the SER and the P2 component of the MP, presumed to represent afferent input from joint and muscle receptors, are attributed to the predominantly post-central projection of the cutaneous afferents which are also activated by electrical stimulation of peripheral nerve.

Summated human EEG potentials with voluntary movement

Abstract Electroencephalographic recordings obtained prior to and during voluntary muscular contractions of human subjects were analyzed by the summation method. A characteristic wave form called the “motor potential” (MP) was found to be associated with foot dorsiflexion and fist contraction. It consisted of 3 major components. Beginning as much as 1 sec prior to contraction, a slow negative shift developed. Frequently, central rhythm blockade occured at this time. The slow potential culminated in an abrupt negative wave having an amplitude of 10–15 μV. The onset of the abrupt negative component occurred 50–150 msec before the first signs of contraction and reached a peak with maximal muscle contraction. This was followed by a late positive deflection that tended to persist for the duration of the contraction. MPs developed concurrently in the two hemispheres with unimanual contraction but differed significantly. Both the abrupt negative wave and the subsequent positive deflection were larger in the hemisphere contralateral to the activated limb. The possibility that the slow negative shift reflected facilitatory events associated with preparation for movement is suggested. The abrupt negative wave is interpreted as a sign of synaptic potentials associated with corticospinal discharge, and the positive deflection may represent afferent, movement-produced feedback.

The functional relation of visual evoked response and reaction time to stimulus intensity

Latency of the average visual evoked response (VER) and motor reaction time (RT) were studied as a function of stimulus intensity for brief photic stimuli subtending 4° and 1.5 of visual angle in two subjects. Both VER latency and RT showed an accelerating increase for each tenfold diminution in intensity down to the region of foveal threshold. Below foveal threshold no responses were obtained for the 1.5° stimuli; there was an inflexion in the VER latency and RT curve of responses to the 4° stimuli. Over the photopic range of intensities, VER latency and RT were closely described by power functions varying in exponent from −0.29 to −0.44. The values for VER were −0.36 for the 4° stimuli and −0.40 for the 1.5° stimuli, which were significantly different ( p < 0.01). Although latency of VER was the same for both subjects for each stimulus condition, RT showed a consistent difference between subjects of about 25 msec. RT is considered to be determined by at least two independent mechanisms. The first, retinal in location, follows a power function of intensity; the second is related to variability in efferent processes.

Patterns of Behavioral Deficit Associated with Visual Spatial Neglect

Summary Visual-spatial neglect as measured by an empirically derived response position preference score on the Raven Coloured Progressive Matrices (RCPM) was examined in 70 patients with cerebral lesions and 63 controls. Patients with right cerebral lesions showed poorer RCPM performance and a higher incidence of response position preference for the side ipsilateral to their lesions than did patients with left lesions. Position preference was significantly associated with homonymous visual field defects, constructional dyspraxia, and in patients with left cerebral lesions mixed or receptive aphasia. The pattern and severity of deficits seemed alike in both right and left lesioned groups. Electroencephalographic evidence indicated that the right lesion group contained a greater number of patients with severe or post-rolandic lesions than did the left lesion group.

Performance of patients with lateralized cerebral lesions. II. Sensory and motor tests.

PERFORMANCE OF PATIENTS WITH LATERALIZED CEREBRAL LESIONS. II: SENSORY AND MOTOR TESTS HERBERT VAUGHAN;LOUIS COSTA; The Journal of Nervous and Mental Disease

Evaluation of the Purdue Pegboard as a Screening Test for Brain Damage

The Purdue Pegboard Test was administered to 183 schoolchildren and to 294 children over six years of age attending pediatric neurology, seizure or endocrine clinics, or a school for educable mentally retarded children. Using suitable cut‐off scores, 180 of 183 normal schoolchildren obtained normal scores, whereas only 23 per cent of children with mental retardation and 22 per cent of those with brain damage did so.

Visual reaction time of patients with cerebral disease as a function of length and constancy of preparatory interval.

Woodrow (1914), Klemrner (1956), and Karlin (1959) have demonstrated chat in normal adults reaction time (RT) is influenced by the duration of the foreperiod or preparatory interval (PI), i.e., the interval between onset of a warning signal and onset of the RT stimulus. Woodrow (1914) found char shorcest RTs were obtained with PIS of 2-sec. duration. Shorter or longer PIS led to RTs of increased length. The normal Ss tested by Rodnick and Shakow ( 1940) also gave evidence that a 2-sec. PI is optimal for RT. Other investigators failed to confirm this finding. They presented evidence thac RT increases with increase in the duration of PI, over a PI range of from .5 to 8 sec. (Klemmer, 1956) and from .5 to 3.5 sec. (Katlin, 1959). Investigation of the relationship of PI to RT has been extended to samples of schizophrenics (Hutson, Shakow, & Riggs, 1937; Rodnick & Shakow, 1940) and to aged patients (Brinley & Botwinic, 1959; Borwinic, Brinley, & Robbin, 1959). These investigators found that their schizophrenic and aged Ss did not respond most rapidly on the RT trials after PIS of 2 sec. or less, as did controls. Furthermore, their patient samples are described as being less able than normals to develop a set for, and respond to, a series of stimuli presented after constant PIS of long duration. While Blackburn and Bencon (1956) and Benton and Joynt (1959) have demonstrated thac RTs in patients with cerebral disease are longer than those of normals when a PI of 2 sec. is used, the effect of differing PIS on the RT of brain-damaged patients has not been reported. The present study is concerned with the following questions: (1) What is the relationship between PI and RT in a series of brain-damaged Ss and in comparable control Ss? (2) What are the effects of repeated trials on the PI-KT relationship? (3) Do control Ss perform more rapidly than brain-damaged Ss on RT casks with PIS other than 2 sec.?

PURDUE PEGBOARD SCORES FOR NORMAL GRAMMAR SCHOOL CHILDREN.

Costa, et al. (1963) have demonstrated the usefulness of the peg placement scores of the Purdue Pegboard as a screening test for cerebral damage in adults. Perceptual motor dysfunction produced by cerebral lesions usually results in performance decrement which is independent of educational background and which is frequently of latetalizing significance. In order to aid in the tests evaluation as a screening procedure for brain damage in children, preliminary norms were established on a sample of 183 normal children attending a Catholic parochial grammar school in New York City. The peg placement section of the test was administered as prescribed in the test manual (SRA, 1948) . One 30-sec. trial was given for each condition. There were no demonstrable differences in performance as a function of sex in 77 female and 8 3 male right-handed children. Norms for males and females combinecl are presented in the table. It seems reasonable to pool scores of all children over 10 as scores change little above this age.

APPLICATION OF EVOKED POTENTIAL TECHNIQUES TO BEHAVIORAL INVESTIGATION.

The development of electronic methods of stimulus presentation and of neuroelectric and behavioral data analysis have, in recent years, provided increasingly powerful tools for the investigation of the neurophysiological correlates of human experience and behavior. A detailed analysis of the neurophysiological events occurring in the interval between stimulus and response should provide insight into the neuronal activity related to the perceptual and cognitive processes preceding action of the organism. Following presentation of visual, somesthetic, o r auditory stimuli, electrical responses may be recorded from the surface ofthe cerebral cortex. Although extensive studies of evoked potentials have been carried out in animals, the value to the behavioral scientist of these observations has been limited, due to the extensive use of general anesthesia whichalters the form and distribution of these responses.1 The depth and type of anesthesia a r e critical, so that a clear picture of the spatial distribution of the various components of cortical responses emerged only recently in studies of unanesthetized animal curarized preparations.2 The behavioral correlates of evoked responses have not, with few exceptions, been observed. It is of considerable interest, therefore, to extend to human subjects observations of cortical evoked potentials while studying subjective and objective responses to varying stimulus parameters under varying states of the organism. The major impetus for investigation of evoked potentials in humans has been the development of reliable electronic methods for the detection of average evoked responses from scalp electrodes. The principle of average response computation is extremely simple, involving the notion that events constantly related in time to a given stimulus will summate when samples of electrical activity a r e added, whereas spontaneous activity which is not constantly related to the stimulus, approach a constant average value. Thus, the average evoked response emerges, after a sufficient number of summated samples, from the progressively flatter baseline of averaged spontaneous activity. Several devices for detection of average evoked responses have been developed, the most flexible and reliable of which have involved the use of analogdigital computers .