In book one chapter 4, it is suggested that there is a special brain region for the recognition faces, to what extend does the evidence in book 4,chapter 2 support this? Explain how the evidence shows that it would be an over simplification to assume that functional organisation of the brain is entirely genetically determined. In your answer state what other factor is more likely to be involved. (No more than 300words) Face recognition is an important specific function of human brain. Moreover, face recognition reflects the specialization nature of human brain. The efficient processing of visual stimuli finally leads to face recognition.
Brain contains fast and dedicated circuits to perform relevant computations required for face recognition. Kanwisher and associates invented fusiform face area (FFA) as potential brain centre for face recognition. The improved versions of the brain image scanning proved that FFA is solely responsible for face recognition. It extracts configural information about faces rather than processing spatial information on the parts of faces. If the FFA is damaged due to injuries to the human brain, the affected patient cannot recognise the faces of even closest people or family members.
However, most recent experiments suggest that FFA is also responsible for recognition of other body parts along with the face. As brain is powerful than a digital camera, at very high scanning resolution processed at this portion, the two separate sub parts will have specialized functions for recognition of face and other body parts. FFA is highly believed to be specialized region for face processing. This also reflects the fine grain structure of human brain and the relevance of recent digital scanning image techniques with high resolution power.
Though the recent schools of thought came up with the linkage of several factors to the face recognition process, earlier there was a strong feeling that it was solely decided by the genetic factors. The role of transduction i. e. the conversion of physical stimuli to neural actions and receptor potential and action potential is very significant in image processing and face recognition. The photoreceptors convert the light energy to neural images. In this way there was over simplification of genetic basis of functional organization of human brain. (293 words). B)
To what extent does the evidence from studies of the FFA support the idea that neural correlate of visual consciousness can be related to the FFA? ( Answer no more than 220words) It is highly proved that the neural correlate of visual consciousness is primarily responsible for the fusiform face area and face recognition. The fine grain structure of the brain facilitates visual consciousness of several neurons. Face recognition comprises of three stages. These stages have linkage to specific regions of the brain. It was found that the inferior occipital gyrus was particularly sensitive to slight physical changes in faces.
Similarly, the right fusiform gyrus (RFG), and the anterior temporal gyrus (ATC), are believed to have connection with th neural processing of visual consciousness and face recoggnition. The sequence of flow of transmission from receptor potential to action potential also supports the link between neural correllate of visual consciousness and FFA. At the same time, the role of photoreceptors in conversion of light energyy to neural image and retinal processing in the form of retinal ganglion cells contribute for the neural correlate of the visual consciousness which in turn is related to the FFA.
The retinal ganglion cells have steady firing rate when visual stimulation is absent where as they exhibit alterations in firing rate durig visual stimulation. This also plays significant role in link between FFA and neural correlate of visual consciousness. (201 words). Question 2 This question relates to the material in book 4 chapter 1,2 and 3 A) State four factors that contributes to the response time of neuronal pathways, giving an explanation for each factor. Give an example of how one of these factors affects speed of transmission in the visual system (Answer no more than 200 words)
In cases of FOK i. e. “feeling of knowing” the people will have a feeling that they know about a particular face but their brain doesn’t make them to recognise. It becomes very common with aging of human beings. The difference in response times of neronal pathways is affected by these factors. It was found that the medial prefrontal cortex exhibited activity during the FOK state, but not when the subjects either knew or did not know a face. Possibly this reflects a state in which subjects were evaluating the correctness of retrieved information.
Additionally, the anterior cingulate area became activated both in the FOK state and when subjects successfully retrieved a name but with some effort. The anterior cingulate area is associated with cognitive conflict processes which allow a person to detect errors in automatic behavior responses. During the recall of personal episodic memories frontal lobes involved in self-awareness and visual memory are actvely engaged . (156 words). B) With the reference to book 4, p. 51 figure 2.
2 identify a location and role for each following: i) receptor potential ii)synaptic potential iii)action potential, giving the main characteristics of each (Answer no more than 250words). Neurons, in general, maintain an electric potential difference across their external membrane. It is caused by a differential distribution of electric charges across the membrane of the cell, living the inside of the cell membrane negative in comparison to the outside. The value of the membrane potential in a given nerve cell may vary from -40 to -80 in different nerve cells. In this process, neurons and muscle cells, can serve as a signaling mechanism.
This also results in an input signal which is known as synaptic potential. Receptor potential is also synonymous with synaptic potential. The excitatory potential is known as receptor potential. Similarly, an integrative signal, occurs mainly at the initial segment of the axon and the axon hillock. A conductive signal is also known as action potential and an output signal is positioned at the synaptic terminal. During the process of stretching, the duration and amplitude of sensory stimulus decides the duration and stimulus of receptor potential. The receptor potential will get converted to action potential at the trigger zone.
The amplitude and duration of receptor potential decides the number and frequency of action potential. Action potential is nothing but the output signal of the neuron. The frequency and pattern potential firing will have remarkable impact on quantity of neurotransmitter released at the action terminal points. (219 words). C) The retinal ganglion cells in book 4 figure 2. 2 p. 51 have input from different types of chemical synapse. One of these cells is depicted schematically in figure 2. 3a. Explain how the input differ in their effects and how these different effects are produced . ( Answer no more than 200 words).
As depicted in Book 4 Figure 2. 2, the retinal ganglion cells of human eye receive different forms of chemical synapse. They receive input from photo receptor cells like rods and cones, outer plexiform layers, inner plexiform layers, amacrine cells, bipolar cells and horizontal cells. In Figure 2. 3 a, the role of photoreceptors in supplying chemical synapse to retinal ganglion cells is depicted well. Different types of retinal ganglion cells encode different visual stimuli. The difference in visual stimulus is resulted by the type of receptor from which chemical synapse is received and the way in which these inputs are wired together.
In the region of lateral geniculate nucleus (LGN) of thalamus, these retinal ganglion cells synapse. There are six layers of neurons in LGN and they receive input from one eye only. They comprise of two ventral layers called magnocellular layers and four dorsal layers known as parvocellular layers receiving different inputs. The retinal ganglion cells form the optic nerve in human eye. (163 words). D) Outline two types of neural network that you might find in the visual system and state the advantage of each (Answer no more than 100words).
Two prominent types of neural net works present in human visual system are magnocellular neural pathway and parvocellular neural pathway. They are also known as M channel and P channels respectively. Magnocellular pathway takes care of ventral portion and parvocellular pathway covers the dorsal portion receiving different inputs resulting in different visual effects. They end in lateral geniculate nucleus, visual cortex and visual chiasma. The advantage of magnocellular pathway is that it connects the 1st and 2nd layers of LGN. Similarly, the parvocellular pathway connects 3rd, 4th , 5th , and 6th layers of LGN. (95 words).
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