Visual-response properties of units in the turtle cerebellar granular layer in vitro

Abstract

1. Single units were recorded extracellularly in the turtle's cerebellar cortex from an isolated brain preparation during visual stimulation. Only a small fraction of the isolated units responded to visual stimuli. For these visually responsive units, the most effective visual stimulus was a moving check pattern that covered the entire surface of the retinal eyecup. The visually responsive units had little or no spontaneous spike activity, nor were they driven by flashes of diffuse light or stationary patterns. 2. All the visually responsive units were direction sensitive and were driven exclusively by the contralateral eye. This direction tuning was well fit by a limaçon model (mean correlation coefficient, 0.89). The distribution of the entire sample indicates a slight preponderance of upward preferred directions. 3. The direction tuning of these cerebellar units was independent of stimulus contrast or the pattern's configuration (such as checkerboards or random check or dot patterns). In the preferred direction, a unit's spike frequency increased monotonically as a function of stimulus velocity until approximately 10 degrees/s, but remained direction sensitive (relative to the opposite direction) at speeds as fast as 100 degrees/s. 4. In some experiments the ventrocaudal brain stem was transected in the frontal plane just caudal to the cerebellar peduncles. Although this lesion presumably removes climbing fiber input from the inferior olivary nuclei, the visual-response properties in the cerebellar cortex were unaffected. 5. The response properties of these units indicate that they encode retinal slip information in the cerebellum.(ABSTRACT TRUNCATED AT 250 WORDS)

Topography and Response Timing of Intact Cerebellum Stained With Absorbance Voltage-Sensitive Dye

“…Second, this preparation uses the turtle's adaptive ability to lower its metabolism even further to survive long dives and a dormant state in water under frozen ponds for many winter months. Recordings from a variety of turtle brain stem regions have demonstrated the very low tonic synaptic and spike activity in this in vitro preparation (Fan et al , 1997Jones and Ariel 2008;Rosenberg and Ariel 1990). Responses in mammalian tissue are more active, even in vitro, so have exhibit more depolarized neuronal membranes on which inhibition can often be measured as a hyperpolarization (Cohen and Yarom 2000a).…”

“…The turtle brain is resistant to hypoxia, permitting topographic analysis of the entire cerebellum in vitro with its brain stem attached. In vitro brain stem neurons are also responsive to natural sensory stimuli: visual patterns imaged on retina Fan et al 1993) and head rotation (Fan et al 1997). The climbing fiber input to turtle Cb was previously investigated using a single micropipette to record extracellular fields following IO microstimulation (Ariel 2005).…”

Morphology of basal optic tract terminals in the turtle, Pseudemys scripta elegans

“…Direction tuning was studied during full-field visual stimuli generated on a video monitor (Amamoto and Ariel, 1993) by using methods described elsewhere (Fan et al, 1993). Sharp micropipettes that successfully impaled BOT axons (criterion was a resting membrane potential Ͼ Ϫ25 mV) had a mean final resistance of 170 M⍀ (ranging between 100 M⍀ and 250 M⍀) when they were filled with 2% neurobiotin (Vector Laboratories, Burlingame, CA) dissolved in 1.0 M potassium methylsulfate.…”

Comparison of visually evoked local field potentials in isolated turtle brain: Patterned versus blank stimulation

“…After being surgically removed from the cranium and bathed in oxygenated artificial cerebrospinal fluid, an intact turtle brain (with eyes attached) can display essentially normal electrophysiological activity in response to visual stimulation (Kriegstein, 1987;Fan et al, 1993). This isolated turtle eye-brain preparation has been extensively used in electrophysiology (Kriegstein, 1987;Fan et al, 1993;Mancilla et al, 1998;Colombe et al, 2004) and optical imaging (Senseman, 1996;Prechtl et al, 1997;Senseman, 1999) in the study of visual function since 1980s.…”