Personal Microbial Cloud Experiment

Humans harbor diverse microbial communities in and on our bodies, and these can be readily detected in the built environment. Human-associated bacteria disperse into and throughout buildings by three primary mechanisms: (1) direct human contact with indoor surfaces; (2) bioaerosol particle emission from our breath, clothes, skin and hair; and (3) resuspension of indoor dust containing previously shed human skin cells, hair and other bacteria-laden particles. Microbial communities in the built environment are often traced back to an individual person, based on their direct contact with an object, including classroom surfaces and mobile phones. Using our unique Climate Chamber, we measured the airborne bacterial emissions, or “microbial cloud“, of individuals. Most occupants could be clearly detected by their cloud or by settled microbial particles within 1.5 – 4 hours. Our results confirm that an occupied space is microbially-distinct from an unoccupied one, and demonstrate for the first time that individuals release their own personalized microbial cloud.

fMRI reveals reciprocal inhibition between social and physical cognitive domains

Two lines of evidence indicate that there exists a reciprocal inhibitory relationship between opposed brain networks. First, most attention-demanding cognitive tasks activate a stereotypical set of brain areas, known as the task-positive network and simultaneously deactivate a different set of brain regions, commonly referred to as the task negative or default mode network. Second, functional connectivity analyses show that these same opposed networks are anti-correlated in the resting state. We hypothesize that these reciprocally inhibitory effects reflect two incompatible cognitive modes, each of which is directed towards understanding the external world. Thus, engaging one mode activates one set of regions and suppresses activity in the other. We test this hypothesis by identifying two types of problem-solving task which, on the basis of prior work, have been consistently associated with the task positive and task negative regions: tasks requiring social cognition, i.e., reasoning about the mental states of other persons, and tasks requiring physical cognition, i.e., reasoning about the causal/mechanical properties of inanimate objects. Social and mechanical reasoning tasks were presented to neurologically normal participants during fMRI. Each task type was presented using both text and video clips. Regardless of presentation modality, we observed clear evidence of reciprocal suppression: social tasks deactivated regions associated with mechanical reasoning and mechanical tasks deactivated regions associated with social reasoning. These findings are not explained by self-referential processes, task engagement, mental simulation, mental time travel or external vs. internal attention, all factors previously hypothesized to explain default mode network activity. Analyses of resting state data revealed a close match between the regions our tasks identified as reciprocally inhibitory and regions of maximal anti-correlation in the resting state. These results indicate the reciprocal inhibition is not attributable to constraints inherent in the tasks, but is neural in origin. Hence, there is a physiological constraint on our ability to simultaneously engage two distinct cognitive modes. Further work is needed to more precisely characterize these opposing cognitive domains.

Exceptional memory

Posits that (1) normal adults with modest amounts of practice can achieve memory performance that equals the recorded performance of people with exceptional memories, (2) the cognitive structures and processes acquired through practice can account for exceptional and expert memory, and (3) all normal adults exhibit skilled and exceptional memory in a domain where they are experts. One undergraduate was administered a digit span task for 1 hr/day, 3–5 times/week, for 20 mo. His digit span steadily improved from 7 to approximately 80 digits. Several other Ss were assessed to determine how information was stored in order to compare them to individuals with exceptional memory. Ss recalled digits in many different matrix patterns. Normal Ss took longer than the trained S and the exceptional Ss to study the matrices. There were no significant time differences between the Ss in ability to retrieve the memorized digits in different orders. Ss retrieved the entire matrix row by row as fast as they retrieved single columns. The trained S reported memorizing the digits using mnemonic associations. It is concluded that there are common components that are characteristic of exceptional memory: prior experience and practice, availability of meaningful associations, and storage and efficient retrieval of information from long-term memory.

Understanding dopamine and reinforcement learning: The dopamine reward prediction error hypothesis | PNAS

A number of recent advances have been achieved in the study of midbrain dopaminergic neurons. Understanding these advances and how they relate to one another requires a deep understanding of the computational models that serve as an explanatory framework and guide ongoing experimental inquiry. This intertwining of theory and experiment now suggests very clearly that the phasic activity of the midbrain dopamine neurons provides a global mechanism for synaptic modification. These synaptic modifications, in turn, provide the mechanistic underpinning for a specific class of reinforcement learning mechanisms that now seem to underlie much of human and animal behavior. This review describes both the critical empirical findings that are at the root of this conclusion and the fantastic theoretical advances from which this conclusion is drawn.

The theory and data available today indicate that the phasic activity of midbrain dopamine neurons encodes a reward prediction error used to guide learning throughout the frontal cortex and the basal ganglia. Activity in these dopaminergic neurons is now believed to signal that a subject’s estimate of the value of current and future events is in error and indicate the magnitude of this error. This is a kind of combined signal that most scholars active in dopamine studies believe adjusts synaptic strengths in a quantitative manner until the subject’s estimate of the value of current and future events is accurately encoded in the frontal cortex and basal ganglia. Although some confusion remains within the larger neuroscience community, very little data exist that are incompatible with this hypothesis. This review provides a brief overview of the explanatory synergy between behavioral, anatomical, physiological, and biophysical data that has been forged by recent computational advances. For a more detailed treatment of this hypothesis, refer to Niv and Montague (1) or Dayan and Abbot (2).

A Symbiotic View of Life: We Have Never Been Individuals

The notion of the “biological individual” is crucial to studies of genetics, immunology, evolution,development, anatomy, and physiology. Each of these biological subdisciplines has a specific conception of individuality, which has historically provided conceptual contexts for integrating newly acquired data. During the past decade, nucleic acid analysis, especially genomic sequencing and high-throughput RNA techniques, has challenged each of these disciplinary definitions by finding significant interactions of animals and plants with symbiotic microorganisms that disrupt the boundaries that heretofore had characterized the biological individual. Animals cannot be considered individuals by anatomical or physiological criteria because a diversity of symbionts are both present and functional in completing metabolic pathways and serving other physiological functions. Similarly, these new studies have shown that animal development is incomplete without symbionts. Symbionts also constitute a second mode of genetic inheritance, providing selectable genetic variation for natural selection. The immune system also develops, in part, in dialogue with symbionts and thereby functions as a mechanism for integrating microbes into the animal-cell community. Recognizing the “holobiont”—the multicellular eukaryote plus its colonies of persistent symbionts—as a critically important unit of anatomy, development, physiology, immunology, and evolution opens up new investigative avenues and conceptually challenges the ways in which the biological subdisciplines have heretofore characterized living entities.

Human emotion and memory: interactions of the amygdala and hippocampal complex

The amygdala and hippocampal complex, two medial temporal lobe structures, are linked to two independent memory systems, each with unique characteristic functions. In emotional situations, these two systems interact in subtle but important ways. Specifically, the amygdala can modulate both the encoding and the storage of hippocampal-dependent memories. The hippocampal complex, by forming episodic representations of the emotional significance and interpretation of events, can influence the amygdala response when emotional stimuli are encountered. Although these are independent memory systems, they act in concert when emotion meets memory.

Amygdala-hippocampus dynamic interaction in relation to memory

Typically the term “memory” refers to the ability to consciously remember past experiences or previously learned information. This kind of memory is considered to be dependent upon the hippocampal system. However, our emotional state seems to considerably affect the way in which we retain information and the accuracy with which the retention occurs. The amygdala is the most notably involved brain structure in emotional responses and the formation of emotional memories. In this review we describe a system, composed of the amygdala and the hippocampus, that acts synergistically to form long-term memories of significantly emotional events. These brain structures are activated following an emotional event and cross-talk with each other in the process of consolidation. This dual activation of the amygdala and the hippocampus and the dynamics between them may be what gives emotionally based memories their uniqueness.


Four experiments are reported which examined memory capacity and retrieval speed for pictures and for words. Single-trial learning tasks were employed throughout, with memory performance assessed by forced-choice recognition, recall measures or choice reaction-time tasks. The main experimental findings were: (I) memory capacity, as a function of the amount of material presented, follows a general power law with a characteristic exponent for each task; (2) pictorial material obeys this power law and shows an overall superiority to verbal material. The capacity of recognition memory for pictures is almost limitless, when measured under appropriate conditions; (3) when the recognition task is made harder by using more alternatives, memory capacity stays constant and the superiority of pictures is maintained; (4) picture memory also exceeds verbal memory in terms of verbal recall; comparable recognition/recall ratios are obtained for pictures, words and nonsense syllables; (5) verbal memory shows a higher retrieval speed than picture memory, as inferred from reaction-time measures. Both types of material obey a power law, when reaction-time is measured for various sizes of learning set, and both show very rapid rates of memory search.

From a consideration of the experimental results and other data it is concluded that the superiority of the pictorial mode in recognition and free recall learning tasks is well established and cannot be attributed to methodological artifact.

Path Dependence, its critics, and the quest for ‘historical economics’

The concept of path dependence refers to a property of contingent, non-reversible dynamical processes, including a wide array of biological and social processes that can properly be described as ‘evolutionary’. To dispel existing confusions in the literature, and clarify the meaning and significance of path dependence for economists, the paper formulates definitions that relate the phenomenon to the property of non-ergodicity in stochastic processes; it examines the nature of the relationship between between path dependence and ‘market failure’, and discusses the meaning of ‘lock-in’. Unlike tests for the presence of non-ergodicity, assessments of the economic significance of path dependence are shown to involve difficult issues of counterfactual specification, and the welfare evaluation of alternative dynamic paths rather than terminal states. The policy implications of the existence of path dependence are shown to be more subtle and, as a rule, quite different from those which have been presumed by critics of the concept. A concluding section applies the notion of ‘lock-in’ reflexively to the evolution of economic analysis, suggesting that resistence to historical economics is a manifestation of ‘sunk cost hysteresis’ in the sphere of human cognitive development.

Making the World Safe for our Children: Down-regulating Defence and Up-regulating Social Engagement to ‘Optimise’ the Human Experience

The Polyvagal Theory helps us understand how cues of risk and safety, which are continuously monitored by our nervous system, influence our physiological and behavioral states. The theory emphasizes that humans are on a quest to calm neural defense systems by detecting features of safety. This quest is initiated at birth when the infant needs for being soothed are dependent on the caregiver. The quest continues throughout the lifespan with needs for trusting friendships and loving partnerships to effectively co-regulate each other. The Polyvagal Theory proposes that through the process of evolution, social connectedness evolved as the primary biological imperative for mammals in their quest for survival. Functionally, social connectedness enabled proximity and co-regulation of physiological state between conspecifics starting with the mother-infant relationship and extending through the lifespan with other significant partners. The theory explains why feeling safe requires a unique set of cues to the nervous system that are not equivalent to physical safety or the removal of threat. The theory emphasizes the importance of safety cues emanating through reciprocal social interactions that dampen defense and how these cues can be distorted or optimized by environmental and bodily cues.