What does the study of brain injury and disease tell us about normal brain functioning?

What does the study of brain injury and disease tell us about normal brain functioning?

Abstract

Although the study of injured and damaged brains dates back to the 19th century, the field of cognitive neuropsychology emerged in the 1960’s, and sought to explain the make up and architecture of normal and intact brains by exploring how the brain breaks down after illness or injury. This paper charts the history of cognitive architecture from inception to modernity, discussing techniques, strengths, shortcomings and modern applications. Although not without issue, it is suggested that imaging techniques such as fMRI will not only continue to expand our knowledge of normal brain functioning, but may have explanatory power in the field of mental disorder,

Introduction

Cognitive psychology is the scientific study of mental functions, and believes such functioning, or cognition, can be explored using the scientific method. It states that all individual components of mental functioning can be identified and understood. Such components are referred to as modules, and therefore any theory regarding the domains of cognition will be a theory of the modules of the system that create the cognitive performance, and a theory of the cognitive architecture of the system. One way in which brain modules and functional architecture can be understood is by studying the way in which the brain breaks down after illness or injury; the science of cognitive neuropsychology.

Main Body

Cognitive neuropsychology emerged as a distinct approach during the 1960’s, but has roots as far back as the 19th century. Pierre Paul Broca’s 1891 post-mortem study of aphasic patient ‘Tan’ who could not produce speech, despite understanding and following directions revealed damage to an area of the frontal lobe (now dubbed ‘Broca’s area’), and provided the first indication that areas of the brain may be specialised for language production.

Commonly cited as the first in the field of cognitive neuropsychology, the series of case studies of patient HM played a crucial role in identifying areas of the brain specific to memory functions (Scoville & Milner, 1957). In 1953, due to severe and untreatable epilepsy, HM had his medial temporal lobes surgically removed. Although successful in treating HM’s epilepsy, he was left with profound yet selective amnesia; specifically anterograde amnesia. Although his working and procedural memory remained intact, he could not commit new information to his long term memory. As the loss of brain matter was surgical, and the damaged areas could be precisely identified, the case of HM revolutionised the study of human memory. In the first, the loss of HM’s medial temporal lobes could be held responsible for his lack of memory, but more crucially, his ability to perform tasks that required recall from short-term and procedural memory, but inability to recall from the long-term memory suggested that different memory processes were mediated by different areas of the brain.

However, these early descriptions of neuropsychological syndromes depended solely on the presentation of neuropsychological deficits and post-mortem analysis. These shortcomings led to the development of the lesion method, the study of patients with lesions to the brain. This involved correlating knowledge of precise damage to the brain with knowledge of specific cognitive impairments.

Although lesion studies allowed for the pinpointing of trauma within the brain (unlike the study of already brain-damaged patients), a major problem was that scientists were unable to confidently claim that lesioned brains mediated cognitive processes identically to intact brains. These led modern theorists came to question the utility of using only damaged brains to explore psychological processes.

Contemporary neuropsychology drew on modern neuroimaging of intact brains to allow considerable developments in the understanding of brain-behaviour relationships. Advancements in techniques such as Positron Emission Tomography (PET) and functional Magnetic Resonance Imaging (fMRI) “led to an explosion in their application in the field of experimental psychology in general and cognitive psychology” (Page 2006; p.429), and the use of fMRI techniques has increased steadily since the outset of their routine use in the early 1990’s. This is for a number of reasons; firstly advances in fMRI techniques have improved their precision, thus the data they produce has become increasingly reliable whilst remaining non-invasive and safer than traditional methods of neuroimaging such as PET (Aue, Lavelle & Cacioppo, 2009). Secondly, they are of particular benefit in studies including human participants, as they allow for the investigation of psychological operations without relying upon verbal reports. This benefit is two-fold; fMRI add of objectivity, whereby verbal reports may be distorted, plus they allow for the investigation of operations to which participants have no verbal access (Aue, Lavelle & Cacioppo, 2009).

Critics of this approach point out that studies relying on imaging techniques are particularly susceptible to inferential errors. Brain activation in one area is inferred as indexing a particular psychological state without considering the antecedent circumstances to that particular activation (Aue, Lavelle & Cacioppo, 2009). Furthermore, some theorists claim that such approaches do not advance psychological theory. As Kilstrom (2006) stated:

“There does not appear to be any instance where neuroscientific findings have constrained social-psychological theory…To the contrary, it appears that precisely the reverse is true: psychological theory constrains the interpretation of neuropsychological and neuroscientific data.” (Kilstrom 2006: p.16)

Despite this, modern imaging techniques have remained the measure of choice in psychological studies of brain activity. Research has seemingly gone full circle to take exciting new directions in the field of cognitive neuropsychiatry. Although in its infancy, researchers have begun to re-apply imaging techniques to the study of disordered individuals. This has led to comprehension of previously misunderstood disorders of face recognition such as prosopagnosia and Capgras Syndrome, and better understanding of brain activity in individuals suffering from a range of mental health problems.

Conclusion

Much can be learnt about the cognitive architecture of the brain by applying findings from brain-injured patients to intact brains. Even the earliest conclusions drawn from case studies in the 19th century endure today. Over time, the sophistication of methods used in cognitive neuropsychology has increased greatly, leading to ever more concrete conclusions regarding the composition, activity and structure of the human brain.

References

Aue, T., Lavelle, L. & Cacioppo, J. (2009). Great expectations: What can fMRI research tell us about psychological phenomenaInternational Journal of Psychophysiology 12 1 – 7.

Broca, Paul. (1861). Nouvelle observation d’aphemie produite par une lesion de la moitie posterieure des deuxieme et troisieme circonvolution frontales gauches. Bulletin de la Societe Anatomique 36 398–407.

Kihlstrom, J.F., 2006. Does neuroscience constrain social–psychological theoryDialogue 21 16 – 17.

Page , M (2006 ). What can’t functional neuroimaging tell the cognitive psychologistCortex 42 (3). 428 – 433.

Scoville, W.B. & Milner, B. (1957). Loss of recent memory after bilateral hippocampal lesions. Journal of Neurology, Neurosurgery and Psychiatry 20 (1) 11 – 21.