Neurophysiology of Learning (Neuroscience of Learning)

The present discourse pertaining to cerebral processing throughout the acquisition of knowledge avails itself of the information processing paradigm, as expounded in Chapter 5 (vide Figure 5.1), as a framework of reference. Cerebral processing during the act of learning is of considerable complexity, and the ensuing exposition shall encompass solely the principal elements thereof. Readers desirous of a more exhaustive treatment of learning and memory from a neurophysiological standpoint are directed to consult supplementary resources (Byrnes, 2001; Jensen, 2005; Rose, 1998; Wolfe, 2001).

The information processing system comprehends sensory registers, short-term (STM) or working memory (WM), and long-term memory (LTM). The sensory registers receive input and retain it for a trifling moment, after which the input is either discarded or channelled to WM. The greater proportion of sensory input is discarded, inasmuch as at any given instant we are assailed with manifold sensory inputs.

Earlier in this chapter, it was observed that all sensory input (save for odours) proceeds directly to the thalamus, whence at least a portion thereof is dispatched to the apposite part of the cerebral cortex for processing (e.g., cerebral lobes that process the fitting sensory information). However, the input is not conveyed in the selfsame guise in which it was received; rather, it is dispatched as a neural “perception” of that input. For instance, an auditory stimulus received by the thalamus shall be transformed into the neural equivalent of the perception of that stimulus. This perception is likewise responsible for collating information to that which is already stored in memory, a process known as pattern recognition. Thus, should the visual stimulus be the classroom pedagogue, the perception conveyed to the cortex shall correspond with the stored representation of the pedagogue, and the stimulus shall be recognised.

A constituent of what renders perception meaningful is that the brain’s reticular activating system filters information to exclude inconsequential details and concentrate on material of import (Wolfe, 2001). This process is adaptive, for were we to attempt to attend to every input, we should never be capable of focusing on aught. There exist several factors that influence this filtering. Perceived importance, such as teachers announcing that material is significant (e.g., will be assessed), is apt to command students’ attention. Novelty attracts attention; the brain tends to focus on inputs that are novel or distinct from what might be anticipated. Another factor is intensity; stimuli that are louder, brighter, or more pronounced garner greater attention. Movement likewise aids in focusing attention. Albeit these attentional systems largely operate unconsciously, it is feasible to employ these notions for assisting in focusing students’ attention in the classroom, such as by employing vivid and novel visual displays.

In summary, sensory inputs are processed in the sensory memories portions of the brain, and those that are retained long enough are transferred to WM. WM appears to reside in multiple parts of the brain but primarily in the prefrontal cortex of the frontal lobe (Wolfe, 2001). As shall be observed in Chapter 5, information is lost from WM in a few seconds unless it is rehearsed or transferred to LTM. For information to be retained, there must exist a neural signal to do so; that is, the information is deemed important and requires to be employed.

The parts of the brain primarily implicated in memory and information processing are the cortex and the medial temporal lobe (Wolfe, 2001). It appears that the brain processes and stores memories in the selfsame structures that initially perceive and process information. Simultaneously, the particular parts of the brain implicated in LTM vary depending on the type of information. A distinction is drawn between declarative memory (facts, definitions, events) and procedural memory (procedures, strategies). Different parts of the brain are implicated in employing declarative and procedural information.

With declarative information, the sensory registers in the cerebral cortex (e.g., visual, auditory) receive the input and transfer it to the hippocampus and the nearby medial temporal lobe. Inputs are registered in much the selfsame format as they appear (e.g., as a visual or auditory stimulus). The hippocampus is not the ultimate storage site; it acts as a processor and conveyor of inputs. As shall be observed in the subsequent section, inputs that occur more often forge stronger neural connections. With multiple activations, the memories form neural networks that become strongly embedded in the frontal and temporal cortexes. LTM for declarative information, therefore, appears to reside in the frontal and temporal cortex.

Much procedural information becomes automatized, such that procedures can be accomplished with little or no conscious awareness (e.g., typing, riding a bicycle). Initial procedural learning implicates the prefrontal cortex, the parietal lobe, and the cerebellum, which ensure that we consciously attend to the movements or steps, and that these movements or steps are assembled correctly. With practice, these areas exhibit less activity, and other brain structures, such as the motor cortex, become more implicated (Wolfe, 2001).

Cognitive neuroscience supports the notion that much can be learnt through observation (Bandura, 1986). Research demonstrates that the cortical circuits implicated in performing an action likewise respond when we observe someone else perform that action (van Gog, Paas, Marcus, Ayres, & Sweller, 2009).

With nonmotor procedures (e.g., decoding words, simple addition), the visual cortex is heavily implicated. Repetition can in sooth alter the neural structure of the visual cortex. These alterations permit us to recognise visual stimuli (e.g., words, numbers) swiftly without consciously having to process their meanings. As a consequence, many of these cognitive tasks become routinized. Conscious processing of information (e.g., pausing to reflect upon what the reading passage means) necessitates extended activity in other parts of the brain.

But what if no meaning can be affixed to an input? What if incoming information, albeit deemed important (such as by a teacher declaring, “Pay attention”), cannot be linked with aught in memory? This situation necessitates the creation of a new memory network, as discussed next.

With repeated presentations of stimuli or information, neural networks may be strengthened, such that the neural responses transpire with alacrity. From a cognitive neuroscience perspective, learning doth involve the formation and reinforcement of neural connections and networks (synaptic connections). This definition doth bear a striking resemblance to the definition of learning in contemporary information processing theories (e.g., ACT-R).

Hebb’s Theory

The process by which these synaptic connections and networks are forged hath been the subject of scientific inquiry for many a year. Hebb (1949) propounded a neurophysiological theory of learning that doth highlight the role of two cortical structures: cell assemblies and phase sequences. A cell assembly is a structure that encompasseth cells in the cortex and subcortical centres (Hilgard, 1956). In essence, a cell assembly is a neural counterpart of a simple association and is formed through oft-repeated stimulations. When a particular stimulation doth recur, the cell assembly is aroused. Hebb maintained that when the cell assembly was aroused, it would facilitate neural responses in other systems, as well as motor responses.

How do cell assemblies form? Hebb could only speculate on this matter, for in his time, the technology for examining brain processes was limited. Hebb surmised that repeated stimulations led to the growth of synaptic knobs, which increased the contact between axons and dendrites (Hilgard, 1956). With repeated stimulations, the cell assembly would be activated automatically, thereby facilitating neural processing.

A phase sequence is a series of cell assemblies. Cell assemblies that are stimulated repeatedly form a pattern or sequence, which imposeth some organisation upon the process. For instance, we are exposed to manifold visual stimuli when we gaze upon the face of a friend. One may conceive of multiple cell assemblies, each of which covereth a particular aspect of the face (e.g., left corner of the left eye, bottom of the right ear). By repeatedly gazing upon the friend’s face, these multiple cell assemblies are simultaneously activated and become connected, to form a coordinated phase sequence that ordereth the parts (e.g., so that we do not transpose the bottom of the right ear onto the left corner of the left eye). The phase sequence alloweth the coordinated whole to be perceived meaningfully and consciously.

Neural Connections

Notwithstanding that Hebb’s ideas are over six decades old, they remain remarkably consistent with contemporary views on how learning occurreth and memories are formed. As we shall observe in the ensuing section on development, we are born with a vast number of neural (synaptic) connections. Our experiences then exert their influence upon this system. Connections are selected or ignored, strengthened or lost. Furthermore, connections can be added and developed through new experiences (National Research Council, 2000).

It is worthy of note that the process of forming and strengthening synaptic connections (learning) doth alter the physical structure of the brain and modify its functional organisation (National Research Council, 2000). Learning specific tasks produceth localised changes in brain areas appropriate for the task, and these changes impose new organisation upon the brain. We are wont to believe that the brain determineth learning, but in truth, there existeth a reciprocal relationship due to the “neuroplasticity” of the brain, or its capacity to alter its structure and function as a result of experience (Begley, 2007).

Although brain research continueth on this important topic, available information indicateth that memory is not formed completely at the moment when initial learning occurreth. Rather, memory formation is a continuous process wherein neural connections are stabilised over a period of time (Wolfe, 2001). The process of stabilising and strengthening neural (synaptic) connections is known as consolidation. The hippocampus appeareth to play a key role in consolidation, despite the fact that the hippocampus is not the locus where memories are stored.

What factors improve consolidation? As discussed in depth in Chapter 5, organisation, rehearsal, and elaboration are important, for they serve to impose a structure. Research doth reveal that the brain, far from being a passive receiver and recorder of information, playeth an active role in storing and retrieving information (National Research Council, 2000).

In summary, it appeareth that stimuli or incoming information activateth the appropriate brain portion and becometh encoded as synaptic connections. With repetition, these connections increase in number and become strengthened, which meaneth that they occur more automatically and communicate better with one another. Learning altereth the specific regions of the brain involved in the tasks (National Research Council, 2000). Experiences are critical for learning, both experiences from the environment (e.g., visual and auditory stimuli) and from one’s own mental activities (e.g., thoughts).

Given that the brain imposeth some structure upon incoming information, it is important that this structure serve to facilitate memory. We might say, then, that simple consolidation and memory are not sufficient to guarantee long-term learning. Rather, instruction should play a key role by helping to impose a desirable structure upon the learning, a point noted by Emma and Claudia in the opening scenario.

The interplay of sundry cerebral structures and synaptic connections doth manifest with particular clarity in the acquisition of language, and pre-eminently in the art of reading. Whilst modern technologies afford researchers the means to scrutinise cerebral function in real-time as individuals assimilate and employ linguistic faculties, a substantial portion of cerebral research concerning language acquisition and utilisation hath been conducted upon individuals who have sustained cerebral trauma and experienced some measure of linguistic impairment. Such inquiry doth illuminate the functions compromised by injury to specific cerebral regions, yet doth not address the matter of language acquisition and employment within the developing brains of children.

Studies of cerebral trauma have evinced that the left hemisphere of the cerebral cortex is of central import to reading, and that the posterior cortical association areas of the said hemisphere are critical for the comprehension and employment of language, and for the execution of normal reading (Vellutino & Denckla, 1996). Dysfunctions of reading are oft symptomatic of lesions in the left posterior cortical regions. Post-mortem examinations of the brains of adolescents and young adults with a history of reading difficulties have revealed structural anomalies within the left hemispheres. Reading dysfunctions are, moreover, sometimes associated with cerebral lesions in the anterior lobes—the region governing speech—albeit the evidence doth more compellingly associate such dysfunctions with abnormalities in the posterior lobes. Given that these findings derive from studies of individuals who possessed (to varying degrees) the faculty of reading, and subsequently suffered some or complete loss thereof, we may conclude that the primarily left-sided regions of the brain, associated with language and speech, are critical to the maintenance of reading.

It is of moment to bear in mind, however, that there existeth no singular, central region of the brain exclusively implicated in reading. Rather, the sundry aspects of reading (e.g., the identification of letters and words, syntax, semantics) involve manifold localised and specialised cerebral structures and synaptic connections, which must be coordinated for the successful execution of reading (Vellutino & Denckla, 1996). The section that followeth shall examine how these interconnections appear to develop both in normal readers and in those afflicted with reading impediments. The prevailing notion is that coordinated reading demandeth the formation of neural assemblies, or collections of neural groups that have established synaptic connections amongst themselves (Byrnes, 2001). Neural assemblies bear a conceptual resemblance to Hebb’s cell assemblies and phase sequences.

Results emerging from neuroscience research demonstrate that specific cerebral regions are associated with the orthographic, phonological, semantic, and syntactic processing requisite for reading (Byrnes, 2001). Orthographic processing (e.g., letters, characters) is heavily reliant upon the primary visual area. Phonological processing (e.g., phonemes, syllables) is associated with the superior temporal lobes. Semantic processing (e.g., meanings) is associated with Broca’s area in the frontal lobe, and with areas in the medial temporal lobe within the left hemisphere. Syntactic processing (e.g., sentence structure) doth also appear to occur within Broca’s area.

We have earlier noted two key regions in the brain implicated in language. Broca’s area playeth a major role in the production of grammatically correct speech. Wernicke’s area (situated in the left temporal lobe below the lateral fissure) is critical for the proper selection of words and elocution. Individuals afflicted with deficiencies in Wernicke’s area may employ an incorrect word, yet one closely related in meaning (e.g., uttering “knife” when “fork” was intended).

Language and reading necessitate the coordination of sundry cerebral regions. Such coordination is affected through bundles of nerve fibres that connect the linguistic areas both to each other and to other parts of the cerebral cortex on both sides of the brain (Geschwind, 1998). The corpus callosum constitutes the largest collection of such fibres, though others exist. Damage to, or destruction of, these fibres impedeth the communication within the brain requisite for proper linguistic function, thereby potentially engendering a language disorder. Cerebral researchers investigate the operational mechanisms of such dysfunctions, and which cerebral functions persist in the presence of damage.

This topic shall be considered further in the ensuing section, by reason of its intimate linkage with cerebral development. For pedagogues, a knowledge of how the brain doth develop is of import, inasmuch as developmental changes must be considered in the planning of instruction, so as to ensure the learning of students.