Cocaine affects cerebral neocortical cytoarchitecture in primates only if administered during neocortical neuronogenesis.

Previously, we demonstrated that chronic exposure of fetal monkeys to cocaine could result in development of the neocortex with significant cytoarchitectonic abnormalities [Synapse, 21 (1995) 435-444]. In the present study, we examined the developmental time-frame within which neocortical cytoarchitecture is susceptible to modifications by prenatal cocaine exposure. For this purpose, we assessed the integrity of cortical lamination and the position, density, and total number of occipital cortical neurons in 2-month-old monkeys which were prenatally exposed to chronic cocaine treatment either prior to the period of neocortical neuronogenesis, during the period of neocortical neuronogenesis, or after the period of neocortical neuronogenesis. We found that cocaine can interfere with the neocortical laminar organization and induce a reduction in the density and number of neocortical neurons only if it is administered at the time of neocortical neuronogenesis. During this window of vulnerability, an abnormal neocortex is generated as long as cocaine exposure is maintained, with corticogenesis becoming normal as soon as the administration of this drug is discontinued.

An eye movement disorder in amyotrophic lateral sclerosis.

Defective pursuit eye movements were recorded by electrooculography (EOG) in 11 of 18 patients (61%) with amyotrophic lateral sclerosis. Pursuit defects consisted of a breakdown of smooth tracking into saccadic motions that were grossly in excess (frequencies and amplitudes) of saccadic interruptions of pursuit in normal subjects. In nine patients, defective pursuits cogwheeling) were obvious by visual inspection as well as by EOG; in two, this abnormality was seen only by EOG. In eight patients, the pursuit defect was the only abnormality of oculomotor function; in three, there were also saccadic defects (optokinetic nystagmus or conjugate gaze) discerned by EOG. Autopsy revealed neuronal degeneration in substantia nigra and demyelination in integral capsule in one patient with the pursuit defect but not in another patient without the defect. The pursuit defect may be a sign of extrapyramidal or supratentorial pyramidal involvement in ALS.

Disappearing palatal myoclonus.

Two patients had palatal myoclonus that disappeared. In one, the palatal myoclonus disappeared completely during all stages of natural sleep only to return again when he awoke, persisting as long as he remained awake. In the other patient, palatal myoclonus was continuous for 2 years, became erratic for 6 months, and then disappeared completely, although she could induce it voluntarily. These cases demonstrate that palatal myoclonus is not always: independent of the sleep-waking cycle, persistent throughout life, and independent of cortical control.

Auditory-visual synesthesia: sound-induced photisms.

Nine patients with visual loss due to lesions of the optic nerve or chiasm experienced photisms induced by sound. Descriptions of these varied from simple flashes of white light to complicated colorful hallucinations likened to a flame, a petal of oscillating lines, a kaleidoscope, or an ameba; they always appeared within a defective portion of the visual field as demonstrated by perimetry. The provoking sounds were usually those of normal daily life, ranged from soft to loud, and always seemed to be heard by the ear ipsilateral to the eye in which the photism was seen. Sound-induced photisms occurred under circumstances that would promote a startle reaction to sound, and each patient was startled when the photisms occurred. Visual evoked responses demonstrated partial deafferentation of the eye in which photisms were seen in seven patients tested. The phenomenon may occur when the patient with a partially deafferent anterior visual pathway is startled by sound.