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Two-Photon Microscopes

As indicated above, powerful microscopes are able to provide an image of the brain as one performs a given task. Two-photon microscopes allow researchers to view activity; however, this is generally limited to study of smaller animals given the size of the microscope and radiation. However, it is possible to theorize human neurobiology from certain small animals such as rats. A constraint of the 2-photon microscope, though, is that it is limited to studying tissue closer to the brain surface than most neural activity occurs.

Hemo-Neural Hypothesis

It is generally held that neurons in the brain facilitate many cognitive processes. Neurons help to transport information from one part of the brain, as it is acquired, to other parts of the brain, where it may be processed. It is generally recognized that this is an electrical process, making electrophysiology a valid approach to studying the brain processes; this is what forms the foundation of computational theories of the mind. The brain is like a computer. Several studies note the relationship between neural disorders and cognition.

Also, the brain includes a vast system of vessels carrying blood to various parts of the brain. Indeed, as Gross (1998) points out, Aristotle believed the manifestation of the activity of this system of veins to be emotion, intelligence, and action (p. 247). Moore and Cao (2008) note that blood flow in the brain “is typically well correlated with neural activity” (p. 2035). As such, they surmise that blood-flow can be an indicator of neural activity, citing several attributes of computational theory and intelligence derived from the Turing Test (Turing, 1950). Moore and Cao (2008, p. 2041) state that,

In many cognitive paradigms, blood flow modulation occurs in anticipation of or independent of the receipt of sensory input. One example of a context in which hemo-neural modulation of cortical dynamics may impact information processing is through enhancement of evoked responses during selective attention. A wide variety of studies has shown that attention to a region of input space (e.g., a retinotopic position or body area) is correlated with enhanced evoked action potential firing of cortical neurons with receptive fields overlapping the attended region (Bichot and Desimone, 2006). These effects typically emerge 100-500 ms after the onset of attentional focus (Khayat et al., 2006; Khoe et al., 2006; Worden et al., 2000). (p. 2041)

In short, they theorize that the connection between neural activity and blood flow is so closely correlated that the two suggest a relationship by which neural activity can be measured by blood flow to certain parts of the brain relative to performance of particular tasks. For example, in highly visual task-oriented studies, a larger amount of blood is observed to flow to the visual (or occipital) cortex than otherwise observed. As such, it is possible to use blood flow—hemodynamics—to study neural activity and cognitive processes. Blood flow can facilitate analysis of neural inhibition (neurons being subdued or prevented from activity) and neural excitation (neural activity increasing). They indicate that fMRI technology allows researchers to observe and measure blood flow and, thus, to infer neurological processes in vivo, important to ascertaining such correlation and analysis (Cao, 2011).

Such findings of correlation between neural activity and blood flow suggest that multiple biological systems are at work within cognition. Much as multimodal rhetoric research has discovered that presenting information using multiple modes may affect cognition better than providing it within a single mode, multiple systems within the brain may be involved in processing information or facilitating such information processing. Rather than one system doing all the work, multiple systems contribute to cognitive processes.

Several studies use this hemo-neural hypothesis to theorize neural processes related to cognition and others use it to triangulate data from EEG methods (see collections edited by Calvert, Spence, and Stein, 2004; and Murray and Wallace, 2012). Further, these studies assert conclusions consistent with studies of multimodal rhetoric, explaining some of the biology behind those conclusions.

The topic of technology has been part of rhetoric and composition scholarship for several years now. Integrating neurobiological studies into the study of the rhetoric of technology opens the door to further analyses of how technologies influence research and contribute to new knowledge about cognitive processes and ways to present information productively to facilitate cognition. Neurobiologists, for example, have studied the ways that simulators affect neural processes, examining blood flow across the brain as subjects interacted with a simulator. Multimodal rhetoric scholars have studied the use of simulators in learning by having subjects perform certain tasks after interacting with a simulator; however, they do not integrate a discussion of neural processes involved in that interaction. Combining research methods and analyses from both fields into a single study may enhance such studies.

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