Basu K. Bagchi

VISUAL EVOKED RESPONSES IN MAN: NORMATIVE DATA.

The fundamental importance of the characteristics of the cerebral electrical response to a simple pulse of light in man is evidenced by the number of workers who have provided information about its features from conventional recordings. Detailed description awaited the development of more powerful analytical tools. With the recognition of the usefulness of photographic superimposition, correlational analysis, and summation techniques (Dawson, 1947; Brazier and Casby, 1951, 1952; Dawson, 1954; Barlow and Brazier, 1954; Brazier and Barlow, 1956), the way was opened for a new phase in the examination of the complexities of cerebral organization. The major features of the visual evoked response have now been outlined by CigLnek, Cobb, Dawson and others. Studies which have included an analysis of latency and polarity of individual components of the response are listed in TABLE 1. The present study was designed to furnish additional information about response morphology, particularly as it might vary in relation to recording site, with the hope that it might lead to an increase in the clinical application of the technique. Also, a preliminary survey of possible relationships between major features of the response and such normal variables as age, eye color, refractive error, color blindness, pupil size, subjective estimate of light intensity, prior nights sleep, alpha frequency, alpha amplitude, and alpha persistence was undertaken.

ELECTROENCEPHALOGRAPHIC PATTERNS OF THE TEMPORAL REGION IN NORMAL ADULTS.

A RECURRENT PROBLEM in the initial evaluation of the patient suspected of having intracranial disease is that of relevance of atypical electrical discharges arising over temporal regions to the disease process in question. Since the studies of Bussel and Silverman? and associates and Obrist and Henry,3 it has been recognized that unilateral or shifting temporal “foci” are much more common in nonneurologically impaired elderly subjects than had been previously supposed. This finding raises a question as to their frequency in normal young and middle-aged adults. The question is fundamental in respect to interpretation of the electroencephalogram, inasmuch as clinical experience indicates that electrographic abnormalities are detected more often over temporal than other cerebral region^.^-^ Not withstanding the major emphasis that has been placed upon electrographic findings for detection of functional disturbances of the temporal lobe in recent years, systematic normative data have not been generally available. This study was undertaken to provide information about incidence, form, and laterality of transient temporal discharges in adults below 60 years of age. The findings have been related to level of alertness of the subject, handedness, other characteristics of the electroencephalographic tracing, and potentially important medical findings.

Temporal or occipital lobe hallucinations triggered from frontal lobe lesions

DIAGKOSIS of a temporal lobe lesion is usually made when the patient has a single or several of the following symptoms: auditory, olfactory, or visual hallucinations, experiential illusions, macropsia, micropsia, dbjd uu phenomena, or automatic movements. T h e question a t once arises i i s to whether this group of symptoms occurs only with temporal lobe involvement or whether it may be obtained from lesions in m y other portion of the cerebral hemisphere and, if so, what the relationship of this second area may be to the temporal lobe. T h e patients whose case histories are reported below, although exhibiting the symptoms risrially regarded as diagnostic of a temporal lobe syndrome, were found a t operation to have frontal lobe involvements.

OBSERVATIONS ON PHOTICALLY EVOKED OCCIPITAL AND VERTEX WAVES DURING SLEEP IN MAN

Information about the character of the visual evoked response in man during sleep and possible differences between waking and sleep is as yet limited. Vanzulli et a2. (1960) reported that response latencies were increased and “positive waves” augmented. CigLnek ( 1961 ) noted that the early triphasic complex was unchanged except for increased latency while a later wave (“V”) was increased in amplitude, broadened and delayed. He observed typical K-complexes during deep sleep. Guillard (1960) has reported that an anteriorly distributed response may persist in sleep when the posterior response has disappeared. He also reported longer response latency as depth of sleep increased. Brazier (1960) and Barlow (1960) have averaged occipital responses to flash in a subject both awake and asleep and have shown that periodic alpha range oscillations may disappear during sleep. The present communication describes morphological characteristics of cerebral responses evoked by single intense photic stimuli presented during sleep, compares these characteristics with those observed in waking and relates response morphology to electrographic and behavioral measures of level of consciousness. Attention is also given to topographical features of the responses, particularly in relation to distinctions that may be drawn between central and occipital events.

Electro-clinical profile of 117 deep cerebral tumors

Many studies report clinical and EEG findings in tumors of deep cerebral structures. It is contended in the main that clinical and radiological data are more useful for diagnosis and localization of such lesions than EEG findings. Workers largely agree on the character and localizing value of EEG in patients with tumors in or near the upper convexity of the brain but they report varied opinions in regard to the deep lesions. One could cull several dozen cases of deep intra-cerebral tumors out of mixed reports in which EEG findings have been described as not outstanding or as not definitely outside normal limits (Broglia and Postir 1956a, b; Daly et al. 1953; Van der Drift 1957; Jus et Jus 1947; Klass and Bickford 1958; Lairy-Bounes et DreyfusBrisac 1950; Lain 1950; Londofio 1957; Longo et al. 1950; Magnus and Van der Drift 1957; McDonald and Korb 1940; Paillas et al. 1948; Parat 1948; Silverman and Graft 1957; Schlesinger and Strauss 1947; T6nnis et al. 1953; Walter and Dovey 1944; Williams 1939). Investigators have found what they consider diffuse and ill-defined EEG abnormalities in these lesions (Bagchi and Bassett 1943; Daly etal . 1953; Longo et al. 1950; Schlesinger and Strauss 1947; Williams and Gibbs 1939). Homolateral alpha depression (Bucy and Case 1940; Case 1940), bilateral alpha bursts (Cobb 1944), fast waves (Cordeau 1959), 14-6/sec positive spikes (Stephenson 1951) have been mentioned.