SEVERAL investigators1-3 have recognized that intermittent visual stimulation such as occurs when the eyes scan a picture is associated in man with the appearance of discrete electric discharges, lambda waves, in the parietal and occipital areas of the scalp. A previous communication4 reported the findings of similar waves in the monkey, dog, cat, and rabbit. Others working with monkeys,5,6 dogs,7 and cats8 also noted the occurrence of discharges in the occipital region, which they likewise considered to be the equivalent of lambda waves in the human.The studies to be reported represent an extension of those previously reported findings.4 Not only were conventional scalp, extradural, and depth recordings made but computer summation techniques also were employed; in particular a Computer of Average Transients (CAT) was triggered by eye-movement potentials, and the succeeding brain activity was summed.9 Thus, it was possible to sum lambda waves of varying size, and the experimenters were able to specify the direction of eye movement-ver¬ tical or horizontal-that would trigger the computer. Another advantage of this tech¬ nique was that comparable recordings could be obtained in the dark as well as in the light, and when the computer was triggered, it was known that an eye movement of spec¬ ified direction had taken place.The following criteria for the recognition of lambda waves were adopted: (1) occur¬ rence of isolated biphasic or triphasic waves in the visual area and adjacent areas occur¬ ring in direct relation to discrete eye move¬ ments, and (2) disappearance of these dis¬ charges when the animal was subjected to a neutral visual field or to darkness, even though eye movements persisted.
Method and MaterialsSince lambda waves represent responses to visual activity and are greatly affected by at¬ tention, the methods employed must not inter¬ fere with visual scansion; this necessarily im¬ plied that observations had to be carried out without the use of anesthetic agents. Because preliminary experiments showed that it was often difficult to obtain satisfactory recordings with scalp electrodes, extradural electrodes were usually employed. These were implanted through small burr holes and connected to a central socket fixed on the apex of the head. A suitable plug with a long lead was used so that the animal could move freely during the recording. It was not necessary to restrict the movements of cats, dogs, rabbits, and guinea pigs. In the case of monkeys in order to avoid active interference with the head plug and cord, it was sometimes desirable to tie the arms to the trunk.The following animals were used: 5 mon¬ keys; 7 cats; 21 dogs; 18 rats; 3 rabbits; and 9 guinea pigs.Electrodes were either placed in burr holes and sealed with acrylic for the larger animals or screwed directly into the skull and support¬ ed by acrylic placed around the screws in the smaller animals. Wires attached to the elec¬ trodes were then soldered to a subminiature socket mounted on a 1-cm flange of acrylic poured over the surface o...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.