The Physiology of High-Order Visual Neurons in the Jumping Spider (Salticidae) and the Vocalizations of Free Ranging Owl Monkeys

Jumping spiders have a highly specialized visual system for the detection and analysis of prey. The retina of each of the anterior medial eyes has a compact, high-resolution, three-dimensional array of receptors that can scan, saccade, and engage in slow tracking. Qualitative study, computer-controlled data collection, and randomized stimulus presentation were used in an electrophysiological study of the properties of high-order visual neurons. Receptive field mapping revealed neurons with well-defined, positionally stable, receptive fields. Some of these receptive fields had an angular extent greater than that of the static retinal array. The stability with respect to the cephalothorax and the angular extent of these receptive fields suggest integration of retinal information and eye position, to yield position constancy. Most neurons had receptive fields of constant angular subtense as the distance to the tangent screen varied. Some neurons have receptive fields that remain relatively constant in absolute physical size (changing in angular extent) as screen distance varies. Such size constant cells may be useful in assessing prey suitability. These characteristics require integration of depth information. These cells are driven monocularly, ruling out disparity cues. Jumping spiders do not use muscular accommodation. Instead, the retina has a layered, tiered structure. Depth of focus cues are probably the source of this information, as hypothesized previously by Land (1969a). Quantitative assessment of velocity preferences revealed cells with medial eye input responding optimally to velocities of 16°/second, and other cells responding to higher velocities. Tuning for direction of movement orientation was also observed and quantified. The degree of tuning correlates with a measure of latency. Results are also presented in a separate section from a primate behavior study on the vocalizations of the owl monkey, in which the vocal repertoire of two populations was recorded. Field recordings were analyzed for temporal and spectral properties of both the vocalizations and the acoustic context. We found no systematic variations of calls between populations, except for the number of syllables in the loud call. We examined behavioral context and probable function of inter and intragroup vocalizations. We found that the loud call may carry gender information, with a bimodal distribution of the spectral bandwidth of the fundamental. This work was supported in part by a National Research Service Award (T32 GM 07737) from the National Institute of General Medical Sciences, and a Lawrence A. Hanson Fellowship.