Neural correlates of visual motion prediction

Predicting the trajectories of moving objects in our surroundings is important for many life scenarios, such as driving, walking, reaching, hunting and combat. We determined human subjects' performance and task-related brain activity in a motion trajectory prediction task. The task required spatial and motion working memory as well as the ability to extrapolate motion information in time to predict future object locations. We showed that the neural circuits associated with motion prediction included frontal, parietal and insular cortex, as well as the thalamus and the visual cortex. Interestingly, deactivation of many of these regions seemed to be more closely related to task performance. The differential activity during motion prediction vs. direct observation was also correlated with task performance. The neural networks involved in our visual motion prediction task are significantly different from those that underlie visual motion memory and imagery. Our results set the stage for the examination of the effects of deficiencies in these networks, such as those caused by aging and mental disorders, on visual motion prediction and its consequences on mobility related daily activities.     

Neural correlates of visual localization and perisaccadic mislocalization

While reading this text, your eyes jump from word to word. Yet you are unaware of the motion this causes on your retina; the brain somehow compensates for these displacements and creates a stable percept of the world. This compensation is not perfect; perisaccadically, perceptual space is distorted. We show that this distortion can be traced to a representation of retinal position in the medial temporal and medial superior temporal areas. These cells accurately represent retinal position during fixation, but perisaccadically, the same cells distort the representation of space. The time course and magnitude of this distortion are similar to the mislocalization found psychophysically in humans. This challenges the assumption in many psychophysical studies that the perisaccadic retinal position signal is veridical.     

Neural circuitry for stimulus selection in the zebrafish visual system

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Neural correlates of the contents of visual awareness in humans

The immediacy and directness of our subjective visual experience belies the complexity of the neural mechanisms involved, which remain incompletely understood. This review focuses on how the subjective contents of human visual awareness are encoded in neural activity. Empirical evidence to date suggests that no single brain area is both necessary and sufficient for consciousness. Instead, necessary and sufficient conditions appear to involve both activation of a distributed representation of the visual scene in primary visual cortex and ventral visual areas, plus parietal and frontal activity. The key empirical focus is now on characterizing qualitative differences in the type of neural activity in these areas underlying conscious and unconscious processing. To this end, recent progress in developing novel approaches to accurately decoding the contents of consciousness from brief samples of neural activity show great promise.     

Neural correlates of visual working memory: fMRI amplitude predicts task performance

We used fMRI to investigate how moment-to-moment neural activity contributes to success or failure on individual trials of a visual working memory (WM) task. We found that different nodes of a distributed cortical network were activated to a greater extent for correct compared to incorrect trials during stimulus encoding, memory maintenance during delays, and at test. A logistic regression analysis revealed that the fMRI signal amplitude during the delay interval in a network of frontoparietal regions predicted successful performance on a trial-by-trial basis. Differential delay activity occurred even for only those trials in which BOLD activity during encoding was strong, demonstrating that it was not a simple consequence of effective versus ineffective encoding. Our results indicate that accurate memory depends on strong sustained signals that span the delay interval of WM tasks.     

Neural correlates of knowledge: stable representation of stimulus associations across variations in behavioral performance

Behavioral responses to a sensory stimulus are often guided by associative memories. These associations remain intact even when other factors determine behavior. The substrates of associative memory should therefore be identifiable by neuronal responses that are independent of behavioral choices. We tested this hypothesis using a paired-associates task in which monkeys learned arbitrary associations between pairs of visual stimuli. We examined the activity of neurons in inferior temporal cortex as the animals prepared to choose a remembered stimulus from a visual display. The activity of some neurons (22%) depended on the monkey's behavioral choice; but for a novel class of neurons (54%), activity reflected the stimulus that the monkey was instructed to choose, regardless of the behavioral response. These neurons appear to represent memorized stimulus associations that are stable across variations in behavioral performance. In addition, many neurons (74%) were modulated by the spatial arrangement of the stimuli in the display.     

Neural correlates of enhanced visual short-term memory for angry faces: an FMRI study

Background

Fluid and effective social communication requires that both face identity and emotional expression information are encoded and maintained in visual short-term memory (VSTM) to enable a coherent, ongoing picture of the world and its players. This appears to be of particular evolutionary importance when confronted with potentially threatening displays of emotion - previous research has shown better VSTM for angry versus happy or neutral face identities.

Methodology/Principal Findings

Using functional magnetic resonance imaging, here we investigated the neural correlates of this angry face benefit in VSTM. Participants were shown between one and four to-be-remembered angry, happy, or neutral faces, and after a short retention delay they stated whether a single probe face had been present or not in the previous display. All faces in any one display expressed the same emotion, and the task required memory for face identity. We find enhanced VSTM for angry face identities and describe the right hemisphere brain network underpinning this effect, which involves the globus pallidus, superior temporal sulcus, and frontal lobe. Increased activity in the globus pallidus was significantly correlated with the angry benefit in VSTM. Areas modulated by emotion were distinct from those modulated by memory load.

Conclusions/Significance

Our results provide evidence for a key role of the basal ganglia as an interface between emotion and cognition, supported by a frontal, temporal, and occipital network.     

Neural correlates of decisions

Once considered the province of philosophy and the behavioral sciences, the process of making decisions has received increasing scrutiny from neurobiologists. Recent research suggests that sensory judgements unfold through the gradual accumulation of neuronal signals in sensory-motor pathways, favoring one alternative over others. Stored representations of the outcome of prior actions activate neurons in many of these same areas during decision-making. The challenge for neurobiologists lies in deciphering how signals from these disparate areas are integrated to form a single behavioral choice and the mechanisms responsible for selecting the appropriate information upon which decisions should be informed in particular contexts.     

Neural correlates of hate

In this work, we address an important but unexplored topic, namely the neural correlates of hate. In a block-design fMRI study, we scanned 17 normal human subjects while they viewed the face of a person they hated and also faces of acquaintances for whom they had neutral feelings. A hate score was obtained for the object of hate for each subject and this was used as a covariate in a between-subject random effects analysis. Viewing a hated face resulted in increased activity in the medial frontal gyrus, right putamen, bilaterally in premotor cortex, in the frontal pole and bilaterally in the medial insula. We also found three areas where activation correlated linearly with the declared level of hatred, the right insula, right premotor cortex and the right fronto-medial gyrus. One area of deactivation was found in the right superior frontal gyrus. The study thus shows that there is a unique pattern of activity in the brain in the context of hate. Though distinct from the pattern of activity that correlates with romantic love, this pattern nevertheless shares two areas with the latter, namely the putamen and the insula.     

Neural correlates of the attentional blink

Attending to a visual event can lead to functional blindness for other events in the visual field. This limit in our attentional capacities is exemplified by the attentional blink (AB), which refers to the transient but severe impairment in perceiving the second of two temporally neighboring targets. Using functional magnetic resonance imaging (fMRI), we observed predominantly right intraparietal and frontal cortex activations associated with the AB. We further demonstrate that an AB can be elicited by both temporal and spatial distractor interference on an attended target and that both of these interference mechanisms activate the same neural circuit. These results suggest that a (right) parietofrontal network previously implicated in attentional control and enhancement is also a locus of capacity-limited processing of visual information.     

Parameters of red blood cell aggregation as correlates of the inflammatory state

To identify clinically relevant parameters of red blood cell (RBC) aggregation, we examined correlations of aggregation parameters with C-reactive protein and fibrinogen in unstable angina (UA), acute myocardial infarction (AMI), and bacterial infection (BI). Aggregation parameters were derived from the distribution of RBC population into aggregate sizes (cells per aggregate) and changing of the distribution by flow-derived shear stress. Increased aggregation was observed in the following order: UA, AMI, and BI. The best correlation was obtained by integration of large aggregate fraction as a function of shear stress. To differentiate plasmatic from cellular factors in RBC aggregation, we determined the aggregation in the presence and absence of plasma and formulated a "plasma factor" (PF) ranging from 0 to 1. In AMI the enhanced aggregation was entirely due to PF (PF = 1), whereas in UA and BI it was due to both plasmatic and cellular factors (0 < or = PF < or = 1). It is proposed that clinically relevant parameters of RBC aggregation should express both RBC aggregate size distribution and aggregate resistance to disaggregation and distinguish between plasmatic and cellular factors.     

Neural correlates of categories and concepts

The ability to readily adapt to novel situations requires something beyond storing specific stimulus-response associations. Instead, many animals can detect basic characteristics of events and store them as generalized classes. Because these representations are abstracted beyond specific details of sensory inputs and motor outputs, they can be easily generalized and adapted to new circumstances. Explorations of neural mechanisms of sensory processing and motor output have progressed to the point where studies can begin to address the neural basis of abstract, categorical representations. Recent studies have revealed their neural correlates in various cortical areas of the non-human primate brain.     

Work of the human visual system. I. Adequate visual stimulus]

It is shown that the adequate stimulus permitting to detect the presence of colour differentiation in the visual field is the change of relative space-time differences of light actions in different retinal points. Differences only in space or only in time are not sufficient for perception.     

Neural correlates of internal-model loading

Skilled object manipulation requires knowledge, or internal models, of object dynamics relating applied force to motion , and our ability to handle myriad objects indicates that the brain maintains multiple models . Recent behavioral studies have shown that once learned, an internal model of an object with novel dynamics can be rapidly recruited and derecruited as the object is grasped and released . We used event-related fMRI to investigate neural activity linked to grasping an object with recently learned dynamics in preparation for moving it after a delay. Subjects also performed two control tasks in which they either moved without the object in hand or applied isometric forces to the object. In all trials, subjects received a cue indicating which task to perform in response to a go signal delivered 5-10 s later. We examined BOLD responses during the interval between the cue and go and assessed the conjunction of the two contrasts formed by comparing the primary task to each control. The analysis revealed significant activity in the ipsilateral cerebellum and the contralateral and supplementary motor areas. We propose that these regions are involved in internal-model recruitment in preparation for movement execution.     

Neural correlates of frog calling

Summary A tissue bath incorporating a screen for support of the specimen and an air-lift pump to circulate saline across the screen was designed to provide maximum exposure of isolated frog brainstems ofRana pipiens pipiens to oxygenated saline (Fig. 1). Normal neural correlates of electrically-evoked mating calling were recorded from the region of the pretrigeminal nucleus and the laryngeal nerve in the isolated brainstem (Fig. 3A) and isolated hemi-brainstem (Fig. 2) of the Northern leopard frog. Conspicuous slow-wave activity in the region of the pretrigeminal nucleus supports the possibility that this may be an important integrative area for calling. It appears that the pretrigeminal region is not able, independently, to generate the pulses of the vocal phase of calling. Synchronizing and reinforcing inter-connections between the calling mechanisms of the two sides were identified. The data are summarized in a revised model of mating calling (Fig. 7).This work was supported by NINDS grant NS-06673. The electronic equipment was set up and maintained by Mr. Wayne R. Hudson. I am grateful to Dr. William Van Meter for suggesting the Sylgard for the pinning block and to Dr. Patricia Gallagher for suggesting the saline solution of Phillis and Tebcis.