Abstract In this work, algorithms have been developed to: 1. Compare visual field coordinate data, presented in different representation systems; 2. Determine the distance in degrees between any two points in the visual field; 3. Predict new coordinates of a given point in the visual field after the rotation of the head, around axes that pass through the nodal point of the eye. Formulas are proposed for the transformation of Polar coordinates into Zenithal Equatorial coordinates and vice versa; of Polar coordinates into Gnomic Equatorial of double meridians and vice versa; and projections of double meridians system into Zenithal Equatorial and vice versa. Using the transformation of polar coordinates into Cartesian coordinates, we can also propose algorithms for rotating the head or the visual field representation system around the dorsoventral, lateral-lateral and anterior-posterior axes, in the mediolateral, dorsoventral and clockwise directions, respectively. In addition, using the concept of the scalar product in linear algebra, we propose new algorithms for calculating the distance between two points and to determine the area of receptive fields in the visual field.

Abstract Abstract: We studied the multiunit responses to moving and static stimuli from 585 cell clusters in area MT using multi-electrode arrays. Our aim was to explore if MT columns exhibit any larger-scale tangential organization or clustering based on their response properties. Neurons showing both motion and orientation selectivity were classified into four categories: 1- Type I (orientation selectivity orthogonal to the axis of motion); 2- Type II (orientation selectivity coaxial to the axis of motion); 3- Type DS (significant response to moving stimuli, but non-significant response to static stimuli); and 4- Type OS (significant orientation selectivity, but non-significant direction selectivity). Type I (34%), Type II (24%) and Type DS (32%) clusters were the most predominant and may be associated with different stages of motion processing in MT. On the other hand, the rarer Type OS (9%) may be integrating motion and form processing. Type I and unidirectional sites were the only classes to exhibit significant clustering. Type OS sites showed a trend for clustering, which did not reach statistical significance. We also found a trend for unidirectional sites to have bidirectional sites as neighbors. In conclusion, neuronal clustering associated with these four categories may be related to distinct MT functional circuits.

Nós investigamos o efeito de uma cena na atividade de células do córtex inferotemporal anterior enquanto o macaco executava uma tarefa de movimento sacádico dos olhos, com e sem o contexto de uma cena (moldura retangular cinza). A maioria dos neurônios não codificou a presença da cena quando ela foi apresentada sozinha no campo visual e o animal estava livre para mover os olhos (macaco na condição de visão livre) ou quando o animal estava fixando um alvo na tela. No entanto, quando um alvo periférico era apresentado e o animal tinha que fazer um movimento sacádico para o alvo, algumas células foram capazes de codificar diferencialmente a presença da cena antes ou depois de um movimento sacádico.

We investigated the effect of a scene on the activity of cells in the anterior inferotemporal (AIT) cortex while the monkey performed a saccadic eye movement (SEM) task with and without the context of a scene (gray frame). Most neurons did not code for the presence of a scene when it appeared alone (monkey free viewing) or when the monkey was fixating. Nevertheless, when a peripheral target was turned on and the monkey had to make a SEM to it, some cells were capable of differentially coding the presence of the scene before and after the saccade.

Estudamos a organização espacial da seletividade ao sentido do movimento na área visual MT do macaco Cebus apella. Utilizamos um arranjo de 6 eletródios paralelos (separados por 700µm) em penetrações tangenciais às camadas corticais para registrar, a cada 200µm, a atividade multi-unitária em resposta a barras em movimento. Determinamos a seletividade ao sentido de movimento em cada sítio de registro. Os dados captados por um único eletródio mostraram uma mudança cíclica e gradual na seletividade ao sentido de movimento dos grupos de neurônios registrados ao longo da trajetória do eletródio, interrompida por mudanças abruptas de 180º ocasionando descontinuidades na seletividade ao sentido do movimento. Para obter mapas de seletividade ao sentido do movimento, examinamos a distribuição espacial da seletividade ao sentido do movimento e aplicamos um método para determinar a localização dos centros dos arranjos radiais formados pela seletividade ao sentido de movimento. Esta organização tangencial é caracterizada por mudanças lentas e contínuas na seletividade ao sentido de movimento interrompida por descontinuidades. As mudanças na seletividade a sentido são organizadas radialmente formando cata-ventos (pinwheels) e bandas de variação linear. Os cata-ventos têm 800 - 1400µm de diâmetro. A cada excentricidade, o tamanho desses arranjos radiais é comparável ao tamanho da imagem de um ponto na área MT.

We studied the spatial organization of direction of motion in visual area MT of the Cebus apella monkey. We used arrays of 6 (700 µm apart) parallel electrodes in penetrations tangential to the cortical layers to record multi-unit responses to moving bars, at 200 µm steps. We determined the direction selectivity at each recording site. The data from single penetrations showed cyclic and gradual changes in the direction selectivity of clusters of cells, intermixed with abrupt 180º discontinuities along the electrode track. In order to obtain maps of direction of motion selectivity, we examined the spatial distribution of direction of motion in MT and we applied a method to determine the location of the centers of radial arrangements of direction selectivity. This tangential organization is characterized by slow continuous changes in direction of motion, interrupted by discontinuities. The changes in direction selectivity are organized radially in a pinwheel fashion and in slabs of linear variation. The pinwheel arrangements have 800-1400 µm in diameter. The size of the radial arrangement is comparable to the point image size in area MT at each eccentricity.