Brain and Cognition 42, 128–130 (2000)
doi:10.1006/brcg.1999.1181, available online at http://www.idealibrary.com on
Mapping Cognitive Processes onto the Brain: Mind the Gap
Diane F. Halpern
California State University, San Bernardino
It is a warning that is familiar to anyone who has traveled the Londonmetro system. At every stop, a recorded message in a British accent cautionstravelers to ‘‘mind the gap’’ between the train and the platform as they enterand leave the subway cars. As commuters rush to their destinations, it iseasy for them to forget that the train and station do not fit together in aseamless connection. I offer the same warning as a caveat for researcherswho are attempting to forge linkages between cognitive and brain processes.It is a tribute to modern advances in understanding cognitive–brain linkagesthat such a warning is even necessary. Like the first riders of the metro whodid not need the warning to watch their step as they moved between thetrain and platform, the pioneers in cognitive neuroscience did not need tobe reminded about the weaknesses in their conclusions about the brain basesof cognition. Thus, I offer the wisdom of ‘‘mind the gap’’ as both a celebra-tion of how far we have come as a discipline and a reminder of how littlestill we know.
The new millennium is a unique landmark in the short history of neurosci-ence because it signifies the close of the much-heralded ‘‘decade of thebrain.’’ The 1990s began with U.S. Congressional recognition that explora-tion into the inner space within the skull was progressing at a rate that mightbe comparable with the speed at which we were moving into outer space.There were and still are good reasons for optimism. New imaging techniquesare allowing us to peer into a functioning human CPU (central processingunit)—older methods like EEGs are becoming more precise and reliable andnewer methods like MRIs and PET scans provide new types of data. For thefirst time, we have the ability to ‘‘see’’ correlates of cognitive processes inintact healthy people as they perform different sorts of cognitive tasks. Formost academics, these advances changed the field of psychology. Psycholog-
Address correspondence and reprint requests to Diane F. Halpern, Department of Psychol-ogy, California State University, San Bernardino, 5500 University Parkway, San Bernardino,CA 92407. E-mail: [email protected].
1280278-2626/00 $35.00Copyright 2000 by Academic PressAll rights of reproduction in any form reserved.
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ical constructs, whose scientific status had been more like ‘‘convenient fic-tions’’ (e.g., the distinction between episodic and semantic memories), nowhave a new brain-based legitimacy. The field of cognitive psychology is dra-matically transformed and terms like ‘‘brain-based’’ education have beenquickly added to the academic and popular jargon. But despite all of theexciting advances, our own knowledge about the relationship between cogni-tion and its underlying biological hardware is in its own perinatal period.The gap between cognition and brain may be more like a chasm, and thereis danger to those of us who believe that bridges are already in place or thatit can leaped in a single bound.
Cognitive Aging—The Next Frontier
As we extrapolate from past trends into the future, there are two relatedtrends that are likely to drive research agendas. Advances in other disciplines(medicine, sanitation) have created the first large cohort of septuagenariansand beyond. The future is old age, both for individuals and society as awhole. The future is also female, with women living an average of sevenyears longer than men. For western, industrialized countries, there have beenhuge increases in the number and proportion of people who are old, and themajority of them are female. At the start of our grandparents’ generation,life expectancy was several decades less than it is for our children. The popu-lation boom in the elderly also means more interest in the cognitive processesof aging and a new emphasis on the role of gonadal hormones in normalhealthy adults. For the first time in history, there are large numbers of adults,especially women, living beyond their reproductive years. The many ques-tions associated with the way gonadal hormones affect cognition in adultsoffer worthy avenues for researchers who are looking for directions for theirresearch in the 2000s. There are now over dozen studies suggesting thatestrogen replacement (commonly referred to as hormone replacement ther-apy, HRT) can have beneficial effects for some aspects of cognition (mostprobably some types of memory) for postmenopausal women and that HRTcauses visible changes in neural structures in the brain. (All of the studieslisted here are discussed and referenced in Halpern, 2000.) HRT also reducesthe probability of Alzheimer’s disease and decreases its severity in womenwho already suffer from this cognitive catastrophe. We know very little aboutthe role of these hormones in aging men or the cognitive consequences ofandrogen replacement in men or women. There is a large body of researchshowing that gonadal hormones are important to cognition at all ages, includ-ing the fact that there are some (on average) sex differences in cognitiveabilities that seem to cross cultural and geographical boundaries. Some as-pects of cognition vary in reciprocal fashion over the menstrual cycle fornormal cycling women and over the day and year in circadian and annualrhythms for normal men. Massive doses of ‘‘cross-sex’’ hormones, adminis-
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tered to individuals who are preparing for sex change surgery also showreciprocal changes in some cognitive processes. These findings have createda lifetime of research questions about the role of gonadal hormones on thebrain and cognition throughout the life span.
Reorganizing for New Questions
Advances in cognitive neuroscience and related fields have widened an-other sort of gap that can be hazardous to our understanding of brain–behav-ior relationships. Researchers are becoming increasingly narrow in their areaof specialization, while at the same time the many questions about gonadalhormone effects on adult cognition require interdisciplinary investigativeteams. The answers to questions about cognitive aging will depend on thenature of the cognitive tasks, the age of the participants, the cognitive, physi-ological, and biological measures that serve as dependent and independentvariables, and the culture and societal milieu in which the studies are con-ducted. To date, there have been very few multidisciplinary investigativeresearch teams working cooperatively to address these broad questions. Thebrain research centers with sophisticated imaging devices are usually man-aged by medical scientists, who lack expertise in the way cognitive tasksdiffer; the other related specializations suffer from the same tunnel visioncreated from viewing the world through their own disciplinary lens. Aca-demic units and funding agencies are organized and funded in ways thatmitigate against interdisciplinary research teams, and the demands of aca-demic tenure and promotion work against long-term projects and collabora-tion across academic units. Future scientists will need a broad education inall of the related disciplines in order to understand the interrelatedness ofgonadal hormones, brain structures and processes, aging, and cognition, frommultiple perspectives. New research questions have created a new need toreorganize higher education and research categorization in ways that promoteinterdisciplinary collaborations.
Third Millennium Perspectives
As we enter the third millennium, those of us excited by new possibilitiesin understanding the brain bases of cognition have much to celebrate, buthumility in the face of recent advances is probably the more appropriateresponse. Both the researchers and the general public need to remember thatwe have only the sketchiest understanding of the way cognitive processesand brain structures and processes interrelate. We are on the verge of findingways to improve cognitive functioning into old age. The future we are seek-ing to improve is ours.
REFERENCE
Halpern, D. F. 2000. Sex differences in cognitive abilities (3rd ed.). Mahwah, NJ: Erlbaum.
