Cerebral cortical and brainstem areas related to the central control of lens accommodation in cat and monkey

Background: We aimed to identify the functional brain networks involved in the regulation of visual accommodation by contrasting the cortical functional areas evoked by foveal fixation to an “E” target, which were subservient to the accommodation responses to a -3/-6 diopter stimulus.Methods: Neural activity was assessed in healthy volunteers by changes in blood oxygen level-dependent (BOLD) signals measured with functional magnetic resonance imaging (fMRI). Twenty-five right-handed subjects viewed the “E” target presented in a hierarchical block design. They participated in two monocular tasks: (i) sustained foveal fixation upon an “E” target on a white background at 33 cm (-3.03D accommodative demand); and (ii) sustained fixation through an attached -3D concave lens (-6D accommodative demand) in front of the fixated eye; each condition cycled through a standard alternating 30-s eye open/30-s eye closed design to provide the BOLD contrast. The total sustained period was 480 s.Results: The contrast between the -3D and the rest condition revealed activation in the occipital lobe (Lingual gyrus, Cuneus, Calcarine_L, and Calcarine_R); cerebellum (Cerebellum_Crus1_L and Cerebellum_6_L); precentral lobe (Precentral_R); frontal lobe (Frontal_Inf_Oper_R and Frontal_Mid_R); and cingulate cortex (Cingulum_Ant_L). With the -3D concave lenses (-6D accommodative demand) in front of the fixated eye, the voxel size and peak intensity of activation in the occipital lobe and cerebellum were greater than with the -3D accommodative demand; emergent activated brain areas included the parietal lobe (bilateral precuneus gyrus and right supramarginal gyrus); the precentral lobe and cingulate cortex failed to reach the threshold in the -6D vs. rest contrast. In the -3D and -6D contrast comparison, the frontal lobe (Frontal_Sup_Medial_L) and parietal lobe (Precuneus_L and Precuneus_R) passed the significance threshold of cluster-level family-wise error (FWE) correction. The mean activation in the -3D and -6D contrast revealed an incremental summation of the activations than that found in the previous -3D vs. rest and -6D vs. rest comparisons.Conclusions: Neural circuits were selectively activated during the -3D/-6D accommodative response to blur cues. Cognitive-perceptual processing is involved in signal regulation of ocular accommodative functions.

Chapter 10 Roles of the lateral suprasylvian cortex in convergence eye movement in cats

Ocular convergence-related neuronal responses in the lateral suprasylvian area of alert cats

Excessive electronic device use has intensified visual workload, resulting in accommodative asthenopia (AA). Our previous functional MRI (fMRI) studies linked abnormal brain function to AA, prompting this resting-state fMRI study to explore local and global brain activity changes. We recruited 33 healthy controls and 44 patients with AA, analyzing regional brain function via coherent regional homogeneity (Cohe-ReHo) and amplitude of low-frequency fluctuation (ALFF)/fractional ALFF (fALFF). Group independent component analysis (gICA) extracted independent components (ICs) for spatial comparison, and static/dynamic functional network connectivity (sFNC/dFNC) assessed subnetwork interactions. Patients with AA had increased ALFF in regions of the right cerebellum 9, superior lobe of the right cerebellum, left cerebellum 8, left cerebellum 9, and left brainstem; there were negative regions in the frontal lobe (also the same area found in fALFF values) and the right postcentral gyrus. Cohe-ReHo was elevated in the inferior lobes of the bilateral cerebellum and left caudate nucleus but reduced in the left median cingulate, paracingulate gyri, and right precentral gyrus. Correlation analysis among Cohe-ReHo, ALFF/fALFF values, and asthenopia survey scores showed that the correlation had no statistical significance. The gICA revealed that the spatial distribution of ICs showed no difference. The results of sFNC and dFNC analysis showed that there was no difference. Patients with AA had regional brain dysfunction. In the analysis of brain subnetworks, there was no difference between the groups in terms of the spatial organization of subnetworks or the static and dynamic connectivity between subnetworks.

Whisker movement has been shown to be under active control in certain specialist animals such as rats and mice. Though this whisker movement is well characterized, the role and effect of this movement on subsequent sensing is poorly understood. One method for investigating this phenomena is to generate artificial whisker deflections with robotic hardware under different movement conditions. A limitation of this approach is that assumptions must be made in the design of any artificial whisker actuators, which will impose certain restrictions on the whisker-object interaction. In this paper we present three robotic whisker platforms, each with different mechanical whisker properties and actuation mechanisms. A feature-based classifier is used to simultaneously discriminate radial distance to contact and contact speed for the first time. We show that whisker-object contact speed predictably affects deflection magnitudes, invariant of whisker material or whisker movement trajectory. We propose that rodent whisker control allows the animal to improve sensing accuracy by regulating contact speed induced touch-to-touch variability.

Many teleosts have an intraocular lens muscle which causes lens movement for visual accommodation. Central pathways for visual accommodation were traced in the filefish ( Novodon modestus ) using horseradish peroxidase (HRP) tracing method. After HRP injection into the lens muscle, large cells were labelled in the ciliary ganglion. After HRP injections into the ciliary ganglion, a compact cell group was retrogradely labelled in an area rostrodorsal to the somatic oculomotor nuclei in the midbrain. The nucleus consisted of about 90 cells which were slightly smaller than the somatic oculomotor neurons. This nucleus was considered to be homologous with the mammalian Edinger-Westphal nucleus. After injections of HRP into the Edinger-Westphal nucleus, cells in the nucleus of the posterior commissure were retrogradely labelled. Because the nucleus of the posterior commissure receives retinal projections (Ito et al. 1984), it is considered that the cells in the nucleus of the posterior commissure are the first central neurons in the pathway for visual accommodation in teleosts.

The purpose of this study was to identify the networks involved in the regulation of visual accommodation/vergence by contrasting the cortical functions subservient to eye-lens accommodation with those evoked by foveal fixation. Neural activity was assessed in normal volunteers by changes in rCBF measured with PET. Thirteen right-handed subjects participated in three monocular tasks: (i) resting with eyes closed; (ii) sustained foveal fixation upon a LED at 1.2 m (0.83 D); and (iii) accommodating alternately on a near (24 cm, 4.16 D) vs. a far (3.0 m, 0.33 D) LED alternately illuminated in sequential 2 s epochs. The contrast between the conditions of near/far accommodation and of constant foveal fixation revealed activation in cerebellar hemispheres and vermis; middle and inferior temporal cortex (BA 20, 21, 37); striate cortex and associative visual areas (BA 17/18). Comparison of the condition of constant fixation with the condition of resting with closed eyes indicated activation of cerebellar hemispheres and vermis; visual cortices (BA 17/18); a right hemisphere dominant network encompassing prefrontal (BA 6, 9, 47), superior parietal (BA 7), and superior temporal (BA 40) cortices; and bilateral thalamus. The contrast between the conditions of near/far accommodation with closed-eye rest reflected an incremental summation of the activations found in the previous comparisons (i.e. activations associated with constant fixation). Neural circuits activated selectively during the near/far response to blur cues over those during constant visual fixation, occupy posterior structures that include occipital visual regions, cerebellar hemispheres and vermis, and temporal cortex.

Extrastriate cortical neurons correlated with ocular convergence in the cat

Functional roles of the lateral suprasylvian cortex in ocular near response in the cat

Three dimensional optometer (TDO) can measure dynamic accommodation, eye movement and pupil diameter simultaneously, while subjects are looking at visual objects by moving their eyes. While three-dimensional visual stimulator (TVS) can present independent binocular targets changing its distance, direction and image size. Using the TDO and the TVS, simultaneous accommodation and vergence responses toward a real image and/or a stereoscopic image created by the TVS were measured. It was found that the accommodation toward the stereoscopic image showed peculiar responses that had less amplitude compared with the response toward the real image, and recede movement of accommodation from the initial peak in the response. A 64-channel whole-cortex magnetoencephalography (MEG) system was also used to study the control mechanism of the accommodation by the central nervous system. A special relay lens system has been developed both to impose visual stimuli and to measure accommodation responses with a dynamic refractometer. Using these systems, MEG and accommodation responses were measured simultaneously. Consequently, an accommodation response toward stepwise stimuli was found after about 300 ms from the onset of the stimuli. Two highly synchronized MEG responses probably related to the accommodative control were found at about 100, 200 ms from the onset of the stimuli prior to the accommodative response.