How do the receptive field properties of magnocellular and parvocellularneurons differ
Howdo the receptive field properties of magnocellular and parvocellularneurons differ? What do the differences imply about their respectiveroles in visual perception?
Howdo the receptive field properties of magnocellular and parvocellularneurons differ?
Magnocellularneurons have larger receptive fields size, higher sensitivity tolow-contrast stimuli, propagate action potentials in a quicker mannerin the optic nerve as compared to parvocellular neurons the former,detect the where properties of visual information while the latterplays an immense role in the perception of color and fine details orform. According to Barret (2011), magnocellular neutrons are lessmodern as compared to the parvocellular ones. Parvocellular neuronshave a higher sensitivity to color and a higher capability ofdiscriminating fine details than magnocellular ones. Magnocellularneurons have higher temporal resolution, but lesser spatialresolution, than the parvocellular ones (Tapia & Breitmeyer,2011). The response of parvocellular neutrons is more tonic andcontinue as long as the stimulus is active, whereas that positiveresponse of magnocellular neutrons to stimulus is composed of a briefsalvo of action potential. Magnocellular neurons take part indetecting movement in a stimulus, whereas parvocellular ones, whichhave small receptive fields, are sensitive to a stimulus details andshape (Tapia et al., 2011)
Whatdo the differences imply about their respective roles in visualperception?
Sincemost parvocellular cells are single color opponent cells, theirresponse to particular wavelengths at the centre of their receptivefields has a high likelihood of being inhibited by the response toanother wavelength that may be in the surroundings (Wright, Colon, &Dyck, 2012). Parvocellular cells that have a red ON-centre and agreen OFF-surround have the green cones occupying the surroundingwhile the red one occupy the centre. Likewise, blue cones are opposedto green and red ones for parvocellular cells with blue-yellowopposition. Wright et al (2012) posits that magnocellular cells lackcolor oppositions since passing of information from the various conesoccur in a simultaneous manner for both the centre and the surround.Indeed, magnocellular cells do not take part in the processing ofcolor since there are no types of these neutrons in the fovea (Hay &Wass, 2009).
Magnocellularneurons play a key role in resolving motion as well as coarseoutlines. Axons of parasol cells, which exit the optic tract, passinformation to these neutrons. Bocanegra & Zeelenberg (2009)argues that the information is then sent to the visual cortices viaoptic radiations. These neurons feed or pass more information to theparietal cortices in the dorsal stream than to the temporal corticesin the ventral stream. Dorsal stream play a key role in therecognizing location of objects in the space and in actions’guidance. It is commonly referred to as ‘where’ or parietalstream and its pathway stretch into the parietal lobe from the visualcortex (primary one). It helps in detecting and analyzing movementssince it has a map of the visual field that is well detailed. In itsinitial function, the dorsal stream carry out visual functions, whileat its termination it carry out the role of spatial awareness. Thisstream has several functioning lobules that act individually (Denison& Silver, 2012). For instance the ventral in raparietal sulcuslay a platform for the integration of somatosensory and visualinformation while the lateral inraparietal sulcus (LIP) is composedof neurons that provide enhanced activation whenever attention isdiverted onto the stimulus or when the animal saccades is divertedtowards a visual stimulus. The neutrons’ system operates atextremely high speed to the expenses of detail. In other words, thissystem is consistent with movement and edges coding rather than tofine detail.
Accordingto Denison et al (2012), parvocellular neurons receive or get theirinput from midget cells, whose axons exit the optic tract. Theprocess of receiving input takes place in one of the four dorsalparvocellular layers of lateral geniculate nucleus. During thisprocess, any information coming from each eye is separate theseparation continues until when the processing occurs in the visualcortex. Relay cells in the optical radiations play a key role inrelaying electrically-encoded visual information from theparvocellular neutrons to the primary visual cortex. Ventral streamis highly linked and associated with formal representation and objectrecognition. In fact, it is mostly referred to as ‘what’ stream.This stream is strongly connected to the medil temporal lobe, thedorsal stream, and limbic system. Limbic system controls emotionswhile the dorsal stream is well known for its ability to deal withmotion and objects. It gets its chief input from parvocellular layerof the lateral geniculate nucleus. It is composed of various neutronswhose receptive fields give a clear representation of the entirevisual field (Bocanegra et al., 2009). All visual information passesthrough the visual cortex (the primary one) before entering theventral stream. Afterwards, the information travels to other areas ina sequential manner. As the information travels to various areas,receptive fields increase the size, the complexity, and latency oftheir tuning. Stimulus’ nature in their receptive field as well asextraetinal factors influence most areas of the ventral stream in anenormous manner. Following this, the ventral stream gives a detaileddescription of the elements as well as plays a significant role inoutlining the importance of these elements.
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