Contrast-sensitivity functions of W-, X-, and Y-like relay cells in the lateral geniculate nucleus of bush baby, Galago crassicaudatus

Abstract

1. This paper represents a continuation of our effort to examine the relationship between the physiology of distinct classes of primate lateral geniculate nucleus (LGN) cells and spatial vision. The present study focuses on modeling the contrast-sensitivity functions (CSFs) of separate LGN cell classes, examining differences in the CSFs of different classes of LGN cells and comparing the results with behaviorally defined CSFs. 2. CSFs to drifting sinusoidal gratings were obtained from single LGN relay cells in the nocturnal primate, Galago crassicaudatus. The CSFs of 14 X-like, 27 Y-like, and 6 W-like cells with standard center-surround organization were well fit by a difference of Gaussians (DOG) model with small residual errors (mean error per data point +/- SEM = 0.008 +/- 0.002). The larger residual errors shown by a few of the Y-like cells were not due to nonlinearity of spatial summation. 3. The CSFs of eight cells that appeared to have nonstandard center-surround organization (primarily, a silent, suppressive surround) were also well fit by the DOG model. 4. The DOG curves that best fitted the data differed considerably between the three groups. As a group, X-like cells had a small center mechanism (Rc = 0.19 degrees) with high sensitivity (Kc = 76.53) and a small, sensitive surround (Rs = 0.71 degrees; Ks = 5.50). These parameters produced CSFs with high cutoff frequencies (Vcutoff = 2.5 c/deg) and low peak sensitivities (CSpk = 6.1) that occurred at 0.8 c/deg. 5. Y-like cells had a large center mechanism (Rc = 0.46 degrees) with low sensitivity (Kc = 21.16) and a large, insensitive surround (Rs = 2.38 degrees; Ks = 0.81). These parameters produced CSFs with lower cutoff frequencies (Vcutoff = 1.2 c/deg) and higher peak sensitivities (CSpk = 12.5) that occurred at 0.2 c/deg. 6. The few W-like cells that responded to gratings well enough to determine a CSF were quite variable. As a group they had a large center mechanism (Rc = 0.38 degrees) with intermediate sensitivity (Kc = 34.55) and a surround with intermediate size and sensitivity (Rs = 1.59 degrees; Ks = 1.59). These produced CSFs with intermediate cutoffs (Vcutoff = 1.6 c/deg) and low peak sensitivities (CSpk = 5.0) occurring at 0.4 c/deg.(ABSTRACT TRUNCATED AT 400 WORDS)

The functional asymmetry of ON and OFF channels in the perception of contrast

“…This potential misclassification, however, does not help explain why the more sensitive (P or K) OFF neurons failed to exhibit any significant choice related activity according to the traditional choice probability measurement. More generally, all LGN cell types likely contribute to some extent to our perception of contrast (Kaplan 2013;Norton et al 1988). Therefore, the functional involvement of the M and K pathways in increment and decrement detections needs to be further investigated in detail and compared with what we have reported here for P ON and P OFF neurons.…”

“…We quantified the peak response amplitude as the highest firing rate of the neuron, z-score normalized in reference to its baseline response. We also computed a transiency index for each neuron, which was very similar to the Phasic/Tonic Index adopted in our previous studies (Irvin et al 1986;Norton and Casagrande 1982;Norton et al 1988). Here the transiency index ϭ 100 Ϫ (100 -200 ms response Ϫ spontaneous response)/(0 -100 ms response Ϫ spontaneous response) ϫ 100.…”

“…Parvocellular (P) cells were distinguished from Magnocellular (M) cells based on their physiological properties together with information about their depth and receptive field locations. According to our previous experience (Norton et al 1988;Royal et al 2006;Xu et al 2001), two of the most reliable classification criteria were visual response latency and transiency (see Jiang et al 2015b for detail). Koniocellular (K) cells were rarely encountered in our recordings, but it is possible that a small proportion of achromatic K cells with good contrast responses were misclassified as P cells in our sample (Roy et al 2009;Solomon et al 2005).…”

“…Even though our experimental work (Jiang et al 2015b) as well as modeling work (Jiang et al 2015a) indicates that P and M neurons work together to code contrast information, we cannot completely discount the possibility that, while increment detection appears to rely on both P ON and M ON neurons, decrement detection may heavily rely on M OFF but not P OFF neurons. As the physiological properties of LGN P and K cell types significantly overlap with each other (for example see Norton et al 1988;Roy et al 2009;White et al 2001;Xu et al 2001), yet another possibility is that a small proportion of P ON and P OFF neurons in our dataset may in fact be K ON and K OFF neurons, respectively. This potential misclassification, however, does not help explain why the more sensitive (P or K) OFF neurons failed to exhibit any significant choice related activity according to the traditional choice probability measurement.…”

Rapid Arrival and Integration of Ascending Sensory Information in Layer 1 Nonpyramidal Neurons and Tuft Dendrites of Layer 5 Pyramidal Neurons of the Neocortex

“…A number of studies have reported that thalamocortical neurons in secondary ascending sensory pathways project their axon to layer 1 (Herkenham, 1979(Herkenham, , 1980Aumann et al, 1998;Huang and Winer, 2000;Mitchell and Cauller, 2001) and unlike those in primary sensory ascending pathways, these neurons show poor receptive fields, labile latencies, and strong dependence on modulatory inputs (Sur and Sherman, 1982;Norton et al, 1988;Diamond et al, 1992;Zhu and Lo, 1998;Ahissar et al, 2000). Surprisingly, whisker stimuli evoke robust synaptic responses in layer 1 neurons and tuft dendrites of layer 5 pyramidal neurons recorded in vivo with a latency of ϳ5-7 msec.…”