Biomedical subjects

H R Maturana

Publications and source records attributed to H R Maturana.

11 recordsLinked to original sources

PubMed1987

Cytoarchitecture of the avian ventral lateral geniculate nucleus.

The avian thalamic ventral lateral geniculate nucleus (GLv) was studied by light microscopic techniques in order to understand its anatomy, neuronal composition, and the nature of its retinal and tectal afferents. The avian GLv is of considerable interest because physiological experiments show that it is the brain structure with the highest percentage of color-opponent responses (Maturana and Varela, '82). We used adult pigeons and quail for the present study. With Nissl techniques a predominance of medium-size neurons (58%) constitute the GLv. The shape, size, and orientation of the different neurons is highly variable throughout the GLv. With the Golgi methods, 5 classes of neurons are distinguished: I and IV (large), II (medium-size), III and V (small). Some class IV large neurons have bifurcated axons; no axons were distinguished on the small neurons. Optic fibers penetrating the GLv are often collateral branches of retinal axons that continue elsewhere. Fink-Heimer methods show that retinal axon terminals end around large and medium-size neurons and also reach the internal lamina of the GLv. HRP tracing shows that the large and medium-size neurons of the GLv project to the optic tectum. On the basis of comparisons between the cytoarchitecture of the GLv described here and the physiological findings previously reported (Maturana and Varela, '82; Pateromichelakis, '79), we suggest that: (1) large GLv neurons are the color-opponent units, (2) medium-size neurons are the movement-sensitive units, and (3) small neurons are either interneurons (local circuit neurons), or they might project to the area pretectalis or to some other GLv projection region not yet described.

Animals↗

PubMed1987

[Perception: behavioral configuration of the object].

The word perception is usually heard as connoting an operation of grasping an external reality through the process of receiving information from it. This, however, is constitutively impossible because living systems are dynamic structure determined systems, and everything happens in them determined at every instant by their structure. This means that the medium cannot specify what happens in a living system, and that it can only trigger in it structural changes determined in its structure. As a result a living system constitutively always operates in structural congruence with the medium, and exists as such only as long as this structural congruence (adaptation) is conserved; otherwise it desintegrates. In these circumstances, the phenomenon connoted by the word perception consists in the association, by the observer, of the behavioral regularities that he or she distinguishes in the observed organism with the conditions of the medium that he or she sees triggering them. The observer uses such behavioral regularities to characterize perceptual objects. This applies to all living systems including the observer. The explanation of perception in the context of the structural determinism of living systems invalidates any attempt to account for the phenomenon of cognition (including language) with notions that entail the denotation or connotation of a domain of reality independent of the distinctions of the observer.

Animals↗

PubMed1984

Regional specialization of the quail retina: ganglion cell density and oil droplet distribution.

The ganglion cell density of the quail's retina was studied in sections and whole mounts. Two regions of high ganglion cell density were found, corresponding to an afoveate area centralis and an area dorsalis. Oil droplets were found to be isotropically distributed throughout the retina. It is proposed that the significance of such retinal regional specialization, in comparison to similar studies in the pigeon and the chick, is that regional specialization in the avian retina is more closely related to feeding habits than to phylogenetic descendence.

Animals↗

PubMed1983

What is it to see?

We as neurobiologists studying vision usually do not ask the question what is it to see? because we considered it a philosophical and not a biological question, and do not realize that we answer it implicitly by doing what we do in our research. This implicit answer entails the basic assumption that we exist in an objective world independent of our acts of cognition and accessible to our knowledge. My contention is: a) that by answering the question what is it to see? one can show that this assumption cannot be sustained because the phenomenon of perception cannot consist in a process of grasping the features of an independent world of objects; and b) that by reflecting upon the nature of a scientific explanation one can show that this assumption is unnecessary because a scientific explanation is a particular kind of coordinations of actions in a community of observers that does not entail it. In this context, a) by putting objectivity in parenthesis, that is, by using the operational generation of scientific explanations and not the object as the criterion of validation of my statements, and, b) by recognizing that the nervous system operates as a closed neuronal network in the generation of its states of activity, I show that the phenomenon of perception arises in the description of an observer as a manner of referring to the operation of an organism in congruence with the particular environment in which it is observed. In these circumstances, my answer to the initial question is: to see is a particular manner of operating as a closed neuronal system component of an organism in a domain of structural coupling. Finally, I propose that by dwelling in language as a peculiar system of coordinations of actions, we human beings bring forth an objective world through using our own changes of states as describers that specify the objects that constitute it.

Adaptation, Physiological↗

PubMed1982

Color-opponent responses in the avian lateral geniculate: a study in the quail (Coturnix coturnix japonica).

Extracellular recordings were made from cells in the ventral lateral geniculate (GLv) of the Japanese quail (Coturnix coturnix japonica), and their responses studied with chromatic stimuli. A total of 156 units were studied, and of these, 124 were found to be optimally responsive to changes in hue, and not to changes of contrast or motion of the stimuli in their receptive fields. These chromatic responses can be characterized as follows: (1) they have large (average 15 degrees x 15 degrees) receptive fields; (2) these receptive fields are mostly located in the anterior part of the visual field; (3) the receptive fields are organized in a (rough) retinotopy in agreement with anatomical findings; (4) units exhibit a sustained response in the dark or under white illumination, which is strongly modulated by changes in hue of stimuli of equal illuminance; (4) the units have a complementary inhibitory response, thus exhibiting a color-opponent pattern of responses; (5) the inhibitory and excitatory areas of the receptive fields are uniform and superimposed; (6) there is a tendency of units of the same optimal chromatic responses to be clustered together in the Glv; (7) although units of all preference are found, the population is dominated by units with preferences in the short wavelength end of the spectrum (48%). This is the first report of a region in the avian brain where color-opponent responses are found in significant numbers, thus making it apparent that the difficulty of finding similar units in the optic tract, tectum, dorsal geniculate, or telencephalon, is not due to a lack of appropriate retinal afferents. The relationship between the present findings and other reports on the Glv's anatomy and physiology are discussed, as well as its possible roles in the generation of chromatic behavioral discrimination of birds.

Animals↗

PubMed1982