Can neuroimaging really tell us what the human brain is doing? The relevance of indirect measures of population activity

Neuroimaging studies using positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) give an indication towards the localization of mental representations and processes in the human brain. It is not clear to what extent such global measures of neuronal activity, pooling across large populations of neurons, can reveal how certain computations are implemented by the neurons in such population ('computational neuroimaging'). Population activity is related tightly to single-cell activity when all neurons in the population have similar response properties. We describe some evidence from single-cell recordings in monkeys that indicates that neurons with similar response properties are not scattered randomly throughout the visual cortex. Notwithstanding this clustering, populations of nearby neurons are still rather heterogeneous, requiring some prudence in deriving single-cell response properties from population activity. The following review of recent neuroimaging studies of the visual system describes to what degree inferences about computations and representations can be drawn from these studies.     

What has fMRI told us about the Development of Cognitive Control through Adolescence?

Cognitive control, the ability to voluntarily guide our behavior, continues to improve throughout adolescence. Below we review the literature on age-related changes in brain function related to response inhibition and working memory, which support cognitive control. Findings from studies using functional magnetic resonance imaging (fMRI) indicate that processing errors, sustaining a cognitive control state, and reaching adult levels of precision, persist through adolescence. Developmental changes in patterns of brain function suggest that core regions of the circuitry underlying cognitive control are on-line early in development. However, age-related changes in localized processes across the brain, and in establishing long range connections that support top-down modulation of behavior, more effective neural processing for optimal mature executive function. While great progress has been made in understanding the age-related changes in brain processes underlying cognitive development, there are still important challenges in developmental neuroimaging methods and the interpretation of data that need to be addressed.     

Individual differences in generalization and imitation: what is the role of brain development?

Jones and Herbert describe research on deferred imitation and how this research reflects on the development of explicit memory in infancy. The article raises several interesting questions about how the medial temporal lobe memory system develops. In this commentary, I discuss some of the additional theoretical and empirical questions that are raised by the target article, and propose ways that these questions could be addressed in future research. Copyright © 2006 John Wiley & Sons, Ltd.     

Visual imagery and memory: Do retrieval strategies affect what the mind's eye sees?

A variety of visual mental imagery tasks have been shown to activate regions of visual cortex that subserve the perception of visual events. Here fMRI was used to examine whether imagery‐related visuocortical activity is modulated if imagery content is held constant but there is a change in the memory retrieval strategy used to invoke imagery. Participants were scanned while visualising common objects in two different conditions: (a) recalling recently encoded pictures and (b) based on their knowledge of concrete nouns. Results showed that retrieval‐related activations in frontal cortex were bilateral when pictures were visualised but left‐lateralised when nouns were visualised. In posterior brain regions, both imagery conditions led to activation in the same set of circumscribed areas in left temporal‐parietal cortex, including a region of the left fusiform gyrus that has previously been implicated in visual imagery. These findings suggest that the posterior network activated during imagery did not vary with strategic task‐related changes in the frontal network used to retrieve imagery content from memory.     

Biological specializations for speech: what can the animals tell us?

Language research over the past 40 years converges on the speech-is-special hypothesis (SiS), according to which speech perception and production are uniquely human adaptations. SiS is grounded in a variety of biological, developmental, and behavioral evidence. In some comparative studies, speechlike stimuli have seemed to cause nonhuman animals to exhibit humanlike performance functions. Auditorists—who believe that spoken language processing is executed by, and is explicable in terms of, general auditory mechanisms—have seized upon such studies as evidence that SiS is incorrect. However, it is difficult to identify biological and functional similarities across different species on the basis of behavior alone, and the elaborate training regimen that nonhuman animals require to achieve human performance levels undermines the significance of certain comparative studies. Both comparative and human behavioral research, including brain-imaging studies of functional localization, electrophysiological recordings of the neural basis of the perception-production link, and developmental studies of a time-locked schedule of language learning, favor SiS over auditorism.     

What can neuroimaging meta-analyses really tell us about the nature of emotion?

In Vytal and Hamann (2010) we reported a neuroimaging meta-analysis that found that basic emotions can be distinguished by their brain activation correlates, in marked contrast to Lindquist et al.'s conclusions in the target article. Here, I discuss implications of these findings for understanding emotion, outline limitations of using meta-analyses and neuroimaging as the sole basis for deciding between emotion views, and suggest that these views are essentially compatible and could be adapted and combined into an integrated emotion framework.     

Authors’ response: what are emotions and how are they created in the brain?

In our response, we clarify important theoretical differences between basic emotion and psychological construction approaches. We evaluate the empirical status of the basic emotion approach, addressing whether it requires brain localization, whether localization can be observed with better analytic tools, and whether evidence for basic emotions exists in other types of measures. We then revisit the issue of whether the key hypotheses of psychological construction are supported by our meta-analytic findings. We close by elaborating on commentator suggestions for future research.     

Decision and experience: why don't we choose what makes us happy?

Recent years have witnessed a growing interest among psychologists and other social scientists in subjective well-being and happiness. Here we review selected contributions to this development from the literature on behavioral-decision theory. In particular, we examine many, somewhat surprising, findings that show people systematically fail to predict or choose what maximizes their happiness, and we look at reasons why they fail to do so. These findings challenge a fundamental assumption that underlies popular support for consumer sovereignty and other forms of autonomy in decision-making (e.g. marriage choice), namely, the assumption that people are able to make choices in their own best interests.     

Propositional unity: what’s the problem, who has it and who solves it?

At least since Russell’s influential discussion in The Principles of Mathematics, many philosophers have held there is a problem that they call the problem of the unity of the proposition. In a recent paper, I argued that there is no single problem that alone deserves the epithet the problem of the unity of the proposition. I there distinguished three problems or questions, each of which had some right to be called a problem regarding the unity of the proposition; and I showed how the account of propositions formulated in my book The Nature and Structure of Content [2007 Oxford University Press] solves each of these problems. In the present paper, I take up two of these problems/questions yet again. For I want to consider other accounts of propositions and compare their solutions to these problems, or lack thereof, to mine. I argue that my account provides the best solutions to the unity problems.     

Visual search for motion-form conjunctions: is form discriminated within the motion system?

Motion-form conjunction search can be more efficient when the target is moving (a moving 45 degrees tilted line among moving vertical and stationary 45 degrees tilted lines) rather than stationary. This asymmetry may be due to aspects of form being discriminated within a motion system representing only moving items, whereas discrimination of stationary items relies on a static form system (J. Driver & P. McLeod, 1992). Alternatively, it may be due to search exploiting differential motion velocity and direction signals generated by the moving-target and distractor lines. To decide between these alternatives, 4 experiments systematically varied the motion-signal information conveyed by the moving target and distractors while keeping their form difference salient. Moving-target search was found to be facilitated only when differential motion-signal information was available. Thus, there is no need to assume that form is discriminated within the motion system.     

Imaging the developing brain: what have we learned about cognitive development?

The human brain undergoes significant changes in both its structural architecture and functional organization across the life span. Advances in neuroimaging techniques over the past decade have allowed us to track these changes safely in the human in vivo. We review the imaging literature on the neurobiology of cognitive development, focusing specifically on cognitive task-dependent changes observed in brain physiology and anatomy across childhood and adolescence. The findings suggest that cortical function becomes fine-tuned with development. Brain regions associated with more basic functions such as sensory and motor processes mature first, followed by association areas involved in top-down control of behavior.     

A general mechanism for decision-making in the human brain?

A new fMRI study by Heekeren and colleagues suggests that left dorsolateral prefrontal cortex (DLPFC) contains a region that integrates sensory evidence supporting perceptual decisions. DLPFC meets two criteria posited by Heekeren et al. for such a region: (1) its activity is correlated in time with the output of sensory areas of the visual cortex measured simultaneously, and (2) as expected of an integrator, its activity is greater on trials for which the sensory evidence is substantial than on trials for which the sensory evidence is weak. Complementary experiments in humans and monkeys now offer a realistic hope of elucidating decision-making networks in the primate brain.     

Dog–human social relationship: representation of human face familiarity and emotions in the dog brain

Animal Cognition - This study investigated the behavioral and neural indices of detecting facial familiarity and facial emotions in human faces by dogs. Awake canine fMRI was used to evaluate...     

Neurolinguistics and neuroimaging: forward to the future,or is it back?

Books reviewed in this article:
Michael Gazzaniga (ed.), Cognitive Neuroscience: A Reader
Alec Marantz, Yasushi Miyashita, and Wayne O'Neil (ed.), Image, Language, Brain: Papers From the First Mind Articulation Project Symposium
Colin Brown and Peter Hagoort, The Neurocognition of Language     

Is the social brain theory applicable to human individual differences? Relationship between sociability personality dimension and brain size

Our study intends to examine whether the social brain theory is applicable to human individual differences. According to the social brain theory primates have larger brains as it could be expected from their body sizes due to the adaptation to a more complex social life. Regarding humans there were few studies about the relationship between theory of mind and frontal and temporal brain lobes. We hypothesized that these brain lobes, as well as the whole cerebrum and neocortex are in connection with the Sociability personality dimension that is associated with individuals' social lives. Our findings support this hypothesis as Sociability correlated positively with the examined brain structures if we control the effects of body size differences and age. These results suggest that the social brain theory can be extended to human interindividual differences and they have some implications to personality psychology too.     

Adlerian-oriented early memory research: what does it tell us?

Of the different approaches to interpreting early memories (EMs), Adlerian-oriented EM research comparatively has shown a most substantial increase in the past 10 years. I examine all Adlerian-oriented EM research appearing from 1981 through 1990. The majority of the research provides a tentative base of support for Adler's (1931) views about EMs. However, several deficiencies in these investigations are identified (e.g., a lack of pilot studies), and some recommendations are made for future EM studies.