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Summary 3.4 B&C - Problem 3: neuroimaging
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1Problem 3 - Neuroimaging
Learning goals
- What can neuroimaging tell us about cognition?
Cooper & Shallice (2010) - Cognitive neuroscience: The troubled marriage of cognitive science
and neuroscience
The emergence of cognitive neuroscience
- 30 years ago cognitive neuroscience was beginning to emerge as a new field of research as
the cognitive was beginning to emerge as a new field of research as the cognitive revolution
began to interact with what were becoming the neurosciences.
- At this time, behavioral neuroscience was well established as physiological
psychology and systems neuroscience was forming out of the interactions between
physiology, anatomy and psychology.
- Physiological psychology/behavioral neuroscience: Focused on
brain-behavior relations.
- Systems neuroscience: Focused on the neural circuits involved in specific
structures.
- Their primary sources of evidence came from animal studies, and although there was
substantial interest in learning, cognitive concepts were peripheral.
- A major transmission route for cognitive concepts was provided by cognitive
neuropsychology. The deficits in neuropsychological patients had begun to be related to
emerging cognitive theories of normal function during the mid-1960s, and by the time
cognitive neuroscience emerged in the late 1970s, the information-processing conceptual
framework was widely applied within cognitive neuropsychology.
- Embryonic cognitive neuroscience was the product of three approaches:
- Physiological psychology/behavioral neuroscience:
- Increasing knowledge of the functional roles of various subcortical structures
and neurotransmitters.
- Wise et al. (1978): proposed a role for dopamine in the reward
system
- Mason & Lin (1980): Noradrenaline plays a role in ignoring irrelevant
stimuli and hence in selective attention.
- Three methodological approaches were standard within the field:
- Chemical studies
- Lesion studies
- Recording of electrical potentials in the scalp (EEG/ERP): this was
the only approach suitable for general use with human subjects, but
at the time this method was not widely used to study cognitive
concepts.
- Systems neuroscience:
- Significant progress had been made in the 1960s and early 1970s in
understanding early sensory processing. This was largely due to Hubel and
Weisel’s pioneering investigations of the receptive fields of cells in the
primary visual cortex of cats and macaque monkeys. However, as this work
primarily involved anaesthetized animals, it was not informed by cognitive
concepts.
- A critical development was the application of single-cell recording to behaving
animals in research that spanned the behavioral and systems approaches,
some of which was directly influenced by cognitive psychology.
, 2
- One key early strand was the work of Fuster & Alexander (1971) who
related the firing of neurons in monkey prefrontal cortex during a
delayed response task to the cognitive concept of short-term
memory.
- At the same time, O’Keefe and Dostrovsky (1971) discovered place
cells in the hippocampus, and this led O’Keefe together with Nadel
(1978) to propose that the hippocampus carries a cognitive map of
the environment.
- Cognitive neuropsychology:
- Much of this at the time aws in neuropsychology, in a revolution stimulated by
the return of a single case study. By the 1970s, it was being applied within
the theoretical framework of the information-processing conception of mental
processes. By the end of that decade, considerable progress had been made
on a variety of fronts.
- The reading system had been fractionated into a set of component
processes. Much was known about the different levels of process
involved in object recognition and how they might break down.
Several systems involved in memory processes had been isolated.
- Much of this work was influenced by the conceptual frameworks
being developed by Marr within cognitive science and Tulving within
cognitive psychology, but the transfer of ideas was bidirectional, with
cognitive neuropsychological studies also leading to major theoretical
developments within more mainstream cognitive psychology.
- It is clear that by the 1980s cognitive concepts had taken hold within cognitive
neuropsychology, and that the transfer of those concepts into neuroscience
had begun.
The development of neuroscience
- Very rapid advances have continued to be made at the cellular and systems levels.
- Within neuropsychology, progress was slower. However, the single case study approach,
combined with developing theory within cognitive psychology, has yielded a more detailed
understanding of the functional architecture underlying a range of cognitive processes. The
group study approach has also seen a resurgence, and new structural imaging methodologies
have brought the brain back into neuropsychology.
- In behavioral neuroscience there has been much progress, for example in understanding the
role and function of subcortical structures, the mechanisms that support neural plasticity and
their consequences, and the effects of specific genes on brain function.
- Within cognitive neuroscience, the single most influential advance for its potential for
understanding cognition has been the advent (=komst) and development of brain-imaging
techniques and methodologies.
- These techniques were borrowed from medicine. Initially, they were only able to
image the brain structure, but in the 1980s Roland et al. (1982) and Fox & Raichle
(1984) used PET to measure differences in regional cerebral blood flow (rCBF) during
cognitive processing. It was argued that rCBF changes in brain regions mirrored the
functioning of those regions during cognitive tasks. PET was dependent on the use of
radioactive tracers.
- A second imaging technique (fMRI), developed in the early 1990s, overcame some of
the problems arising from this dependence. fMRI detects differences in blood
oxygenation, a variable that relates to neural activity without the need for a
radioactive tracer. Many refinements in fMRI analysis and experimental design over
the past 20 years greatly extended the utility of brain imaging.
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- adoption of statistically standardized methods of analysis and reporting.
- Adoption of standardized brain templates beginning with the Talairach atlas
- Use of event-related designs
- There have been many other significant technological advances, such as MEG and
high density ERP, TMS, and a range of further imaging techniques. The existence of
this range of techniques is valuable because each has different properties with
respect to the degree of temporal and spatial localization of neural activity. At the
same time, the range and costs of techniques now available has greatly affected the
sociology of cognitive neuroscience
- A further development that has had a large impact on part of the field is the rise of
computational modeling.
- Connectionism found a natural home in cognitive neuropsychology, where
they had early success in modeling deficits in reading typical of some
acquired dyslexia.
- Connectionism has made far less contact with fMRI than with
neuropsychology. Connectionist models generally do not naturally
have a correspondence to anatomical localizations.
- Modeling also played an important role in both systems neuroscience and
behavioral neuroscience, and modelers with a concern for neurobiological
data have developed increasingly complex computational accounts of
subcortical structures and circuits within the prefrontal cortex.
How have these methodological developments affected the field?
- The range of techniques available in fMRI escalates exponentially each year.
- In areas such as ‘thinking’ cognitive neuroscience methods have become standard.
- New areas such as executive functions/cognitive control, social cognition and
neuroeconomics have proliferated.
- This represents genuine progress, not just fashion.
The future of cognitive neuroscience
It is now possible to combine fMRI with other methods, including TMS, EEG, and NIRS. There is also
increasing use of techniques such as diffusion weighted imaging and dynamic causal modeling to
establish effective connectivity within the brain.
Further progress is likely to involve the integration of developments in additional fields, such as
cellular and genetic advances linked into our understanding of brain and cognitive processes.
There are dangers which threaten to derail progress. A group of cognitive neuropsychologists have
argued that functional imaging for all its technical sophistication has failed to lead to any increased
understanding at the cognitive level of analysis (Coltheart). Coltheart has posed a challenge to
cognitive neuroscientists to provide examples where definitive answers to open theoretical questions
have been given by functional imaging evidence. So far, there has been no conclusive response.
- Cooper & Shallice believe that this perspective on functional imaging is too limited. However,
they believe that there are also grave sociological dangers, possibly exemplified by the
division between the cognitive science & the cognitive neuroscience societies. The complexity
of the mind, the brain and the relation between the two means that approaching any research
question from a single perspective limits the inferences that can be made. Moreover, the
relative lack of power of behavioral data means that any development based on a single
result or method is likely to be open to multiple interpretations
→ It is this weak power of behavioral evidence that gives Coltheart’s arguments their
apparent force.
, 4
The biological roots of neuroscience mean that it tends not to view the mind from the perspective of
Marr’s (1982) most critical level processing and knowledge-producing machine. The field risks being
driven too much by the technically sweet possibilities that arise from new and improved technologies,
rather than by scientific questions aimed a teasing apart different cognitive theories or extending our
cognitive understanding of specific processes.
This threat is compounded by a reductionist risk → that the concepts and theoretical progress of the
cognitive revolution are forgotten as teams with
different types of empirical expertise attempt to
reverse engineer the brain though increasingly
sophisticated techniques.
In the author’s view, if cognitive neuroscience focuses too much on the neuroscience at the expense
of the cognitive, then not only will its contribution to cognitive science be marginalized, but also will it
be unable to make sense of the increasing masses of brain-based data now being generated. The
use of well designed cognitive tasks based on cognitive theory will be critical.
Sociological issues:
- The rise of combined methods continues to push toward big science. As research becomes
more resource intensive, it becomes more centralized and as a consequence probably less
cognitive.
Ethical and legal issues:
- Questions are raised by the increasing possibility of using neuroimaging techniques to detect
otherwise private mental phenomena for business, forensic, or political purposes.
Despite these concerns, there remains a host of scientific questions that a genuinely cognitive
neuroscience is well placed to answer over the coming decades. There is still no single area of
cognition for which we have a standardly accepted theoretical account.
Cognitive neuroscience, despite its dangers, if applied in a non reductionist style, offers the potential
to enable cognitive science to achieve the status of a Kuhnian normal science by establishing a
generally agreed theoretical framework.
Definitions
- Reductionism: Phenomena that are described in terms of other simpler or more fundamental
phenomena.
Mahy, Moses & Pfeifer (2014) - How and where: Theory-of-mind in the brain
Introduction:
Current state of ToM (Theory of Mind) research
- There is little overlap in how developmental psychologists and social neuroscientists study the
ways in which people impute mental states to self and other.
- Social neuroscience and developmental psychology both prominently feature research on
ToM, yet emphasize different facets of this core social cognitive ability:
- Social neuroscience: where in the brain mentalizing resides
- Developmental psychology: How mentalizing is acquired (and when it emerges)
- As a result, much of the adult neuroimaging work has not been explicitly linked to
developmental theories; instead, it has focused on identifying ToM-relevant neural regions,
and distinguishing groups of individuals such as those with and without autism spectrum
disorders in terms of systems or processes recruited.
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