Functional connectivity during working memory maintenance

Neurophysiological experiments with monkeys have demonstrated that working memory (WM) is associated with persistent neural activity in multiple brain regions, such as the prefrontal cortex (PFC), the parietal cortex, and posterior unimodal association areas. WM maintenance is believed to require the coordination of these brain regions, which do not function in isolation but, rather, interact to maintain visual percepts that are no longer present in the environment. However, single-unit physiology studies and traditional univariate analyses of functional brain imaging data cannot evaluate interactions between distant brain regions, and so evidence of regional integration during WM maintenance is largely indirect. In this study, we utilized a recently developed multivariate analysis method that allows us to explore functional connectivity between brain regions during the distinct stages of a delayed face recognition task. To characterize the neural network mediating the on-line maintenance of faces, the fusiform face area (FFA) was defined as a seed and was then used to generate whole-brain correlation maps. A random effects analysis of the correlation data revealed a network of brain regions exhibiting significant correlations with the FFA seed during the WM delay period. This maintenance network included the dorsolateral and ventrolateral PFC, the premotor cortex, the intraparietal sulcus, the caudate nucleus, the thalamus, the hippocampus, and occipitotemporal regions. These findings support the notion that the coordinated functional interaction between nodes of a widely distributed network underlies the active maintenance of a perceptual representation.     

Memory,past and self

The purpose of this essay is to determine how we should construe the content of memories. First, I distinguish two features of memory that a construal of mnemic content should respect. These are the ‘attribution of pastness’ feature (a subject is inclined to believe of those events that she remembers that they happened in the past) and the ‘attribution of existence’ feature (a subject is inclined to believe that she existed at the time that those events that she remembers took place). Next, I distinguish two kinds of theories of memory, which I call ‘perceptual’ and ‘self-based’ theories. I argue that those theories that belong to the first kind but not the second one have trouble accommodating the attribution of existence. And theories that belong to the second kind but not the first one leave the attribution of pastness unexplained. I then discuss two different theories that are both perceptual and self-based, which I eventually reject. Finally, I propose a perceptual, self-based theory that can account for both the attribution of pastness and the attribution of past existence.     

The neural bases of distracter-resistant working memory

A major difference between humans and other animals is our capacity to maintain information in working memory (WM) while performing secondary tasks, which enables sustained, complex cognition. A common assumption is that the lateral prefrontal cortex (PFC) is critical for WM performance in the presence of distracters, but direct evidence is scarce. We assessed the relationship between fMRI activity and WM performance within subjects, with performance matched across distracter and no-distracter conditions. Activity in the ventrolateral PFC during WM encoding and maintenance positively predicted performance in both conditions, whereas activity in the presupplementary motor area (pre-SMA) predicted performance only under distraction. Other parts of the dorsolateral and ventrolateral PFCs predicted performance only in the no-distracter condition. These findings challenge a lateral-PFC-centered view of distracter resistance, and suggest that the lateral PFC supports a type of WM representation that is efficient for dealing with task-irrelevant input but is, nonetheless, easily disrupted by dual-task demands.     

Knowledge and abilities: The need for a new understanding of knowing-how

Stanley and Williamson (The Journal of Philosophy 98(8), 411–444 2001) reject the fundamental distinction between what Ryle once called ‘knowing-how’ and ‘knowing-that’. They claim that knowledge-how is just a species of knowledge-that, i.e. propositional knowledge, and try to establish their claim relying on the standard semantic analysis of ‘knowing-how’ sentences. We will undermine their strategy by arguing that ‘knowing-how’ phrases are under-determined such that there is not only one semantic analysis and by critically discussing and refuting the positive account of knowing-how they offer. Furthermore, we argue for an extension of the classical ‘knowing-how’/‘knowing-that’-dichotomy by presenting a new threefold framework: Using some core-examples of the recent debate, we will show that we can analyze knowledge situations that are not captured by the Rylean dichotomy and argue that, therefore, the latter has to be displaced by a more fine-grained theory of knowledge-formats. We will distinguish three different formats of knowledge we can have of our actions, namely (1) propositional, (2) practical, and (3) image-like formats of knowledge. Furthermore, we will briefly analyze the underlying representations of each of these knowledge-formats.     

Modality and domain specific components in auditory and visual working memory tasks

In the tripartite model of working memory (WM) it is postulated that a unique part system—the visuo-spatial sketchpad (VSSP)—processes non-verbal content. Due to behavioral and neurophysiological findings, the VSSP was later subdivided into visual object and visual spatial processing, the former representing objects’ appearance and the latter spatial information. This distinction is well supported. However, a challenge to this model is the question how spatial information from non-visual sensory modalities, for example the auditory one, is processed. Only a few studies so far have directly compared visual and auditory spatial WM. They suggest that the distinction of two processing domains—one for object and one for spatial information—also holds true for auditory WM, but that only a part of the processes is modality specific. We propose that processing in the object domain (the item’s appearance) is modality specific, while spatial WM as well as object-location binding relies on modality general processes.     

Age differences in prefrontal cortical activity in working memory

Working memory (WM) declines with advancing age. Brain imaging studies indicate that ventral prefrontal cortex (PFC) is active when information is retained in WM and that dorsal PFC is further activated for retention of large amounts of information. The authors examined the effect of aging on activation in specific PFC regions during WM performance. Six younger and 6 older adults performed a task in which, on each trial, they (a) encoded a 1- or 6-letter memory set, (b) maintained these letters over 5-s. and (c) determined whether or not a probe letter was part of the memory set. Comparisons of activation between the 1- and 6-letter conditions indicated age-equivalent ventral PFC activation. Younger adults showed greater dorsal PFC activation than older adults. Older adults showed greater rostral PFC activation than younger adults. Aging may affect dorsal PFC brain regions that are important for WM executive components.     

The role of alpha oscillations in deriving and maintaining spatial relations in working memory

Previous research has demonstrated distinct neural correlates for maintenance of abstract, relational versus concrete, sensory information in working memory (WM). Storage of spatial relations in WM results in suppression of posterior sensory regions, which suggests that sensory information is task-irrelevant when relational representations are maintained in WM. However, the neural mechanisms by which abstract representations are derived from sensory information remain unclear. Here, using electroencephalography, we investigated the role of alpha oscillations in deriving spatial relations from a sensory stimulus and maintaining them in WM. Participants encoded two locations into WM, then after an initial maintenance period, a cue indicated whether to convert the spatial information to another sensory representation or to a relational representation. Results revealed that alpha power increased over posterior electrodes when sensory information was converted to a relational representation, but not when the information was converted to another sensory representation. Further, alpha phase synchrony between posterior and frontal regions increased for relational compared to sensory trials during the maintenance period. These results demonstrate that maintaining spatial relations and locations in WM rely on distinct neural oscillatory patterns.     

Sensing Aliveness

This study examines whether the categories animate/inanimate might be formed on the basis of information available to the cognitive system. We suggest that the discrimination of percepts according to these categories relies on proprioceptive information, which allows the perceiving subject to know that he is ‘animate’. Since other ‘objects’ in the world exhibit movements, reactions, etc. similar to those that the subject experiences himself, he can ‘project’ his knowledge onto these objects and recognize them as ‘animate’ like himself. On this basis we try to corroborate the empricist position in the debate concerning the organization of knowledge as opposed to the nativist view. Furthermore, we argue that the categorical dichotomy animate/inanimate is more basic than other analogous ones such as living/non-living, biological/non-biological and we sketch a ‘categorical stratification’ following the line ‘humans–animals–plants’ based on the hypothesis that humans detect different degrees of ‘vitality’ according to the degree of similarity they recognise between the considered instance and themselves.     

Neuroimaging studies of working memory:

We performed meta-analyses on 60 neuroimaging (PET and fMRI) studies of working memory (WM), considering three types of storage material (spatial, verbal, and object), three types of executive function (continuous updating of WM, memory for temporal order, and manipulation of information in WM), and interactions between material and executive function. Analyses of material type showed the expected dorsal-ventral dissociation between spatial and nonspatial storage in the posterior cortex, but not in the frontal cortex. Some support was found for left frontal dominance in verbal WM, but only for tasks with low executive demand. Executive demand increased right lateralization in the frontal cortex for spatial WM. Tasks requiring executive processing generally produce more dorsal frontal activations than do storage-only tasks, but not all executive processes show this pattern. Brodmann’s areas (BAs) 6, 8, and 9, in the superior frontal cortex, respond most when WM must be continuously updated and when memory for temporal order must be maintained. Right BAs 10 and 47, in the ventral frontal cortex, respond more frequently with demand for manipulation (including dual-task requirements or mental operations). BA 7, in the posterior parietal cortex, is involved in all types of executive function. Finally, we consider a potential fourth executive function: selective attention to features of a stimulus to be stored in WM, which leads to increased probability of activating the medial prefrontal cortex (BA 32) in storage tasks.     

Quantifiers and propositional attitudes: Quine revisited

Quine introduced a famous distinction between the ‘notional’ sense and the ‘relational’ sense of certain attitude verbs. The distinction is both intuitive and sound but is often conflated with another distinction Quine draws between ‘dyadic’ and ‘triadic’ (or higher degree) attitudes. I argue that this conflation is largely responsible for the mistaken view that Quine’s account of attitudes is undermined by the problem of the ‘exportation’ of singular terms within attitude contexts. Quine’s system is also supposed to suffer from the problem of ‘suspended judgement with continued belief’. I argue that this criticism fails to take account of a crucial presupposition of Quine’s about the connection between thought and language. The aim of the paper is to defend the spirit of Quine’s account of attitudes by offering solutions to these two problems. See also chapters four and five of Word and Object (Quine, 1960) and ‘Intensions Revisited’ (Quine, 1977).     

What is an emotional feeling? Lessons about affective origins from cross-species neuroscience

Cross-species affective neuroscience aspires to provide an evidence-based foundation for understanding the primary-process emotional networks that concurrently control instinctual emotional actions and affective feelings—direct emotional circuit mediated ‘rewards’ and ‘punishments’. In humans and other mammals, the ancestral subcortical regions of the brain are central to such affective BrainMind functions (a monistic term, here used synonymously with MindBrain, depending on stylistic needs). Although these circuits cannot be ‘identical’ across species (that would be incompatible with evolutionary principles) they are sufficiently similar, anatomically, neurochemically and functionally, to allow animal brain research to illuminate (yield testable predictions) about homologous human mind functions. Primal emotional feelings (affects) are inbuilt value functions of the brain that energize and inform the rest of the mental apparatus about basic survival values, thereby promoting secondary-process learning/memory functions and tertiary-process cognitive thinking-ruminative functions, yielding bottom-up evolutionary controls that ultimately allow top-down regulatory controls. As we envision how such “nested” hierarchies—two-way paths of causality—reflecting both bottom-up and top-down functions—we will need disciplined distinctions between cognitions and emotions at the primary-process level, while also accepting total interpenetrance of cognitions and affects at the tertiary-process level of MindBrain organization. This allows full and synergistic integration of basic and dimensional approaches to emotions. Here the primal emotional networks, so critically important for understanding ‘human-nature’ and psychiatric disorders, are discussed didactically in ways that can minimize dilemmas that non-evolutionary, non-hierarchical perspectives are subject to in modern emotion research.     

On Mill,Infallibility, and Freedom of Expression

Philosophers have tended to dismiss John Stuart Mill’s claim that ‘all silencing of discussion is an assumption of infallibility’. I argue that Mill’s ‘infallibility claim’ is indeed open to many objections, but that, contrary to the consensus, those objections fail to defeat the anti-authoritarian thesis which lies at its core. I then argue that Mill’s consequentialist case for the liberty of thought and discussion is likewise capable of withstanding some familiar objections. My purpose is to suggest that Mill’s anti-authoritarianism and his faith in thought and discussion, when taken seriously, supply the basis for a ‘public interest’ account of ‘freedom of expression as the liberty of thought and discussion’ which is faithful to Mill in spirit, if not to the precise letter. I outline such an account, which – as I say in conclusion – can serve as a valuable safeguard against ad hoc, reactive legislation, and the demands of a spurious communitarianism.     

A Note on Irrelevance in Inductive Logic

We consider two formalizations of the notion of irrelevance as a rationality principle within the framework of (Carnapian) Inductive Logic: Johnson’s Sufficientness Principle, JSP, which is classically important because it leads to Carnap’s influential Continuum of Inductive Methods and the recently proposed Weak Irrelevance Principle, WIP. We give a complete characterization of the language invariant probability functions satisfying WIP which generalizes the Nix–Paris Continuum. We argue that the derivation of two very disparate families of inductive methods from alternative perceptions of ‘irrelevance’ is an indication that this notion is imperfectly understood at present.     

A Defence of the Asymmetry in Population Ethics

A common intuition is that there is a moral difference between ‘making people happy’ and ‘making happy people.’ This intuition, often referred to as ‘the Asymmetry,’ has, however, been criticized on the grounds that it is incoherent. Why is there, for instance, not a corresponding difference between ‘making people unhappy’ and ‘making unhappy people’? I argue that the intuition faces several difficulties but that these can be met by introducing a certain kind of reason that is favouring but non-requiring. It is argued that there are structural similarities between the asymmetry and moral options and that the asymmetry can be defended as an instance of a moral option.     

Development of dopaminergic genetic associations with visuospatial,verbal and social working memory

Dopamine transmission in the prefrontal cortex (PFC) supports working memory (WM), the temporary holding, processing and manipulation of information in one's mind. The gene coding the catechol‐O‐methyltransferase (COMT) enzyme, which degrades dopamine, in particular in the PFC, has a common single nucleotide polymorphism leading to two versions of the COMT enzyme which vary in their enzymatic activity. The methionine (Met) allele has been associated with higher WM performance and lower activation of the PFC in executive function tasks than the valine (Val) allele. In a previous study, COMT genotype was associated with performance on verbal and visuospatial WM tasks in adults, as well as with performance on a novel social WM paradigm that requires participants to maintain and manipulate information about the traits of their friends or family over a delay. Here, data collected in children and adolescents (N = 202) were compared to data from the adult sample (N = 131) to investigate possible age differences in genetic associations. Our results replicate and extend previous work showing that the pattern of superior WM performance observed in Met/Met adults emerges during development. These findings are consistent with a decrease in prefrontal dopamine levels during adolescence. Developmentally moderated genetic effects were observed for both visuospatial and social WM, even when controlling for non‐social WM performance, suggesting that the maintenance and manipulation of social information may also recruit the dopamine neurotransmitter system. These findings show that development should be considered when trying to understand the impact of genetic polymorphisms on cognitive function.     

Working memory and the attentional blink: Blink size is predicted by individual differences in operation span

The attentional blink (AB) is often attributed to resource limitations, but the nature of these resources is commonly underspecified. Recent observations rule out access to short-term memory or storage capacity as limiting factors, but operation bottlenecks are still an option. We considered the operation span of working memory (WM) as a possible factor and investigated the relationship between individual WM operation span (as measured by OSPAN), fluid intelligence (as measures by Raven’s SPM), and the size of the AB. WM operation span was negatively correlated with the AB, whereas fluid intelligence was associated with higher overall accuracy but not with AB magnitude. These results support the idea that individual processing limitations (with regard to either attentional allocation policies or the speed of global cortical integration processes) play a key role in the AB.     

Motive and Right Action

Some philosophers believe that a change in motive alone is sometimes sufficient to bring about a change in the deontic status (rightness or wrongness) of an action. I refer to this position as ‘weak motivism’, and distinguish it from ‘strong’ and ‘partial motivism’. I examine a number of cases where our intuitive judgements appear to support the weak motivist’s thesis, and argue that in each case an alternative explanation can be given for why a change in motive brings about (or, in some cases, appears to bring about) a change in deontic status.     

Levinas on suffering and compassion

This paper provides an analysis of suffering and compassion in the work of Emmanuel Levinas. Levinas describes compassion as ‘the nexus of human subjectivity’ and the ‘supreme ethical principle’. In his early texts, suffering discloses the burden of being, the limits of the self, and thus the approach of alterity. Levinas’s later phenomenology of suffering as passive, meaningless, and evil, functions as a refutation of rational explanations of suffering. I argue that Levinasian substitution, the traumatic election to an excessive responsibility, is the compassionate suffering that Levinas terms the nexus of human subjectivity. For Levinas, ethics is the compassionate response to the vulnerable, suffering Other.     

Talking About a Universalist World

The paper defends a combination of perdurantism with mereological universalism by developing semantics of temporary predications of the sort ’some P is/was/will be (a) Q’. We argue that, in addition to the usual application of causal and other restrictions on sortals, the grammatical form of such statements allows for rather different regimentations along three separate dimensions, according to: (a) whether ‘P’ and ‘Q’ are being used as phase or substance sortal terms, (b) whether ‘is’, ‘was’, and ‘will be’ are the ‘is’, ‘was’, ‘will be’ of identity or of constitution, and (c) whether ‘Q’ is being used as a subject or predicate term. We conclude that this latitude is beneficial, as it conforms with linguistic reality (i.e., the multiple uses actually in place) and also enables one to turn what is ordinarily perceived as a problem for universalist perdurantism viz., a commitment to all sorts of weird and gerrymandered temporally extended entities, into an advantage, for the richness in questions allows us to make sense of the many different readings of sentences of the same grammatical form.     

Domain specificity in the primate prefrontal cortex

Experimental studies in nonhuman primates and functional imaging studies in humans have underlined the critical role played by the prefrontal cortex (PFC) in working memory. However, the precise organization of the frontal lobes with respect to the different types of information operated upon is a point of controversy, and several models of functional organizations have been proposed. One model, developed by Goldman-Rakic and colleagues, postulates a modular organization of working memory based on the type of information processing (the domain specificity hypothesis). Evidence to date has focused on the encoding of the locations of visual objects by the dorsolateral PFC, whereas the ventrolateral PFC is suggested to be involved in processing the features and identity of objects. In this model, domain should refer to any sensory modality that registers information relevant to that domain—for example, there would be visual and auditory input to a spatial information processing region and a feature analysis system. In support of this model, recent studies have described pathways from the posterior and anterior auditory association cortex that target dorsolateral spatial-processing regions and ventrolateral object-processing regions, respectively. In addition, physiological recordings from the ventrolateral PFC indicate that some cells in this region are responsive to the features of complex sounds. Finally, recordings in adjacent ventrolateral prefrontal regions have shown that the features of somatosensory stimuli can be discriminated and encoded by ventrolateral prefrontal neurons. These discoveries argue that two domains, differing with respect to the type of information being processed, and not with respect to the sensory modality of the information, are specifically localized to discrete regions of the PFC and embody the domain specificity hypothesis, first proposed by Patricia Goldman-Rakic.