A head view-invariant representation of gaze direction in anterior superior temporal sulcus

Humans show a remarkable ability to discriminate others' gaze direction, even though a given direction can be conveyed by many physically dissimilar configurations of different eye positions and head views. For example, eye contact can be signaled by a rightward glance in a left-turned head or by direct gaze in a front-facing head. Such acute gaze discrimination implies considerable perceptual invariance. Previous human research found that superior temporal sulcus (STS) responds preferentially to gaze shifts [1], but the underlying representation that supports such general responsiveness remains poorly understood. Using multivariate pattern analysis (MVPA) of human functional magnetic resonance imaging (fMRI) data, we tested whether STS contains a higher-order, head view-invariant code for gaze direction. The results revealed a finely graded gaze direction code in right anterior STS that was invariant to head view and physical image features. Further analyses revealed similar gaze effects in left anterior STS and precuneus. Our results suggest that anterior STS codes the direction of another's attention regardless of how this information is conveyed and demonstrate how high-level face areas carry out fine-grained, perceptually relevant discrimination through invariance to other face features.     

Control of visuotemporal attention by inferior parietal and superior temporal cortex

The human cortical visual system is organized into major pathways: a dorsal stream projecting to the superior parietal lobe (SPL), considered to be critical for visuospatial perception or on-line control of visually guided movements, and a ventral stream leading to the inferotemporal cortex, mediating object perception. Between these structures lies a large region, consisting of the inferior parietal lobe (IPL) and superior temporal gyrus (STG), the function of which is controversial. Lesions here can lead to spatial neglect, a condition associated with abnormal visuospatial perception as well as impaired visually guided movements, suggesting that the IPL+STG may have largely a "dorsal" role. Here, we use a nonspatial task to examine the deployment of visuotemporal attention in focal lesion patients, with or without spatial neglect. We show that, regardless of the presence of neglect, damage to the IPL+STG leads to a more prolonged deployment of visuotemporal attention compared to lesions of the SPL. Our findings suggest that the human IPL+STG makes an important contribution to nonspatial perception, and this is consistent with a role that is neither strictly "dorsal" nor "ventral". We propose instead that the IPL+STG has a top-down control role, contributing to the functions of both dorsal and ventral visual systems.     

A higher order motion region in human inferior parietal lobule: evidence from fMRI

The proposal that motion is processed by multiple mechanisms in the human brain has received little anatomical support so far. Here, we compared higher- and lower-level motion processing in the human brain using functional magnetic resonance imaging. We observed activation of an inferior parietal lobule (IPL) motion region by isoluminant red-green gratings when saliency of one color was increased and by long-range apparent motion at 7 Hz but not 2 Hz. This higher order motion region represents the entire visual field, while traditional motion regions predominantly process contralateral motion. Our results suggest that there are two motion-processing systems in the human brain: a contralateral lower-level luminance-based system, extending from hMT/V5+ into dorsal IPS and STS, and a bilateral higher-level saliency-based system in IPL.     

Integration of auditory and visual information about objects in superior temporal sulcus

Two categories of objects in the environment-animals and man-made manipulable objects (tools)-are easily recognized by either their auditory or visual features. Although these features differ across modalities, the brain integrates them into a coherent percept. In three separate fMRI experiments, posterior superior temporal sulcus and middle temporal gyrus (pSTS/MTG) fulfilled objective criteria for an integration site. pSTS/MTG showed signal increases in response to either auditory or visual stimuli and responded more to auditory or visual objects than to meaningless (but complex) control stimuli. pSTS/MTG showed an enhanced response when auditory and visual object features were presented together, relative to presentation in a single modality. Finally, pSTS/MTG responded more to object identification than to other components of the behavioral task. We suggest that pSTS/MTG is specialized for integrating different types of information both within modalities (e.g., visual form, visual motion) and across modalities (auditory and visual).     

Activation in posterior superior temporal sulcus parallels parameter inducing the percept of animacy

An essential, evolutionarily stable feature of brain function is the detection of animate entities, and one of the main cues to identify them is their movement. We developed a model of a simple interaction between two objects, in which an increase of the correlation between their movements varied the amount of interactivity and animacy observers attributed to them. Functional magnetic resonance imaging revealed that activation in the posterior superior temporal sulcus and gyrus (pSTS/pSTG) increased in relation to the degree of correlated motion between the two objects. This activation increase was not different when subjects performed an explicit or implicit task while observing these interacting objects. These data suggest that the pSTS and pSTG play a role in the automatic identification of animate entities, by responding directly to an objective movement characteristic inducing the percept of animacy, such as the amount of interactivity between two moving objects.     

Projections from cortical visual areas of the superior temporal sulcus to the superior colliculus, in macaque monkeys.

1. The distribution of tectal projections of two visual areas of the superior temporal sulcus (MT and MST areas) has been studied, in five Macaca fascicularis, by means of the autoradiographic method tracing the anterograde transport of tritiated aminoacids intracortically injected. 2. In all cases the ipsilateral superior colliculi (SC) were found labelled, whereas the contralateral ones were devoid of label. 3. The three brains injected in the MT area resulted in SC labels that involved the superficial gray layer (SGS), the stratum opticum (SO) and the intermediate gray layer (SGI), sparing the layers below SGI. 4. The collicular labels found after injections within the MST area exhibited their distribution over the deep SC subdivision, whereas they spared all the superficial layers but the deep part of the SO. 5. In two animals with large uptake zones, one in MT and the other in MST, the labelling within the SGI showed a cluster-like pattern. 6. The distinct found bulk of projections of MT and MST respectively to the superficial and deep subdivisions of the SC, along with a number of peculiar connections of the MST area as mentioned in the text, contribute to depict an overall neural network in which MST appears to be more strongly involved than MT in linking sensory visual with oculomotor attentive functions.     

Morphological patterns of the intraparietal sulcus and the anterior intermediate parietal sulcus of Jensen in the human brain

Distinct parts of the intraparietal sulcal cortex contribute to sensorimotor integration and visual spatial attentional processing. A detailed examination of the morphological relations of the different segments of the complex intraparietal sulcal region in the human brain in standard stereotaxic space, which is a prerequisite for detailed structure-to-function studies, is not available. This study examined the intraparietal sulcus (IPS) and the related sulcus of Jensen in magnetic resonance imaging brain volumes registered in the Montreal Neurological Institute stereotaxic space. It was demonstrated that the IPS is divided into two branches: the anterior ramus and the posterior ramus of the IPS, often separated by a submerged gyral passage. The sulcus of Jensen emerges between the anterior and posterior rami of the IPS, and its ventral end is positioned between the first and second caudal branches of the superior temporal sulcus. In a small number of brains, the sulcus of Jensen may merge superficially with the first caudal branch of the superior temporal sulcus. The above morphological findings are discussed in relation to previously reported functional neuroimaging findings and provide the basis for future exploration of structure-to-function relations in the posterior parietal region of individual subjects.     

Neural responses in human superior temporal cortex support coding of voice representations

The ability to recognize abstract features of voice during auditory perception is an intricate feat of human audition. For the listener, this occurs in near-automatic fashion to seamlessly extract complex cues from a highly variable auditory signal. Voice perception depends on specialized regions of auditory cortex, including superior temporal gyrus (STG) and superior temporal sulcus (STS). However, the nature of voice encoding at the cortical level remains poorly understood. We leverage intracerebral recordings across human auditory cortex during presentation of voice and nonvoice acoustic stimuli to examine voice encoding at the cortical level in 8 patient-participants undergoing epilepsy surgery evaluation. We show that voice selectivity increases along the auditory hierarchy from supratemporal plane (STP) to the STG and STS. Results show accurate decoding of vocalizations from human auditory cortical activity even in the complete absence of linguistic content. These findings show an early, less-selective temporal window of neural activity in the STG and STS followed by a sustained, strongly voice-selective window. Encoding models demonstrate divergence in the encoding of acoustic features along the auditory hierarchy, wherein STG/STS responses are best explained by voice category and acoustics, as opposed to acoustic features of voice stimuli alone. This is in contrast to neural activity recorded from STP, in which responses were accounted for by acoustic features. These findings support a model of voice perception that engages categorical encoding mechanisms within STG and STS to facilitate feature extraction.

Voice perception occurs via specialized networks in higher order auditory cortex, but how voice features are encoded remains a central unanswered question. Using human intracerebral recordings of auditory cortex, this study provides evidence for categorical encoding of voice.     

Projections from the cortex of the superior temporal sulcus to the dorsal lateral geniculate and pregeniculate nuclei in the macaque monkey

Cortical projections from the visual region and adjacent polysensory region of the superior temporal sulcus (STs) to the lateral geniculate body (LGb) were investigated in the macaque monkey using an autoradiographic tracing method. Solutions of tritiated aminoacids were injected into different parts of the caudal half of the STs of five animals. A survival time of 7 days was allowed. Labels were found in both subdivisions of the LGb: the dorsal lateral geniculate nucleus (DLGn) and the pregeniculate nucleus (PGn). In particular, part of the visual cortical region adjacent to the middle temporal area (MT) projects into the DLGn as well as the PGn, whereas the MT itself and the superior temporal polysensory region project into the PGn only. Afferents to the DLGn terminate in the magnocellular layers and in their adjoining interlaminar zones, completely sparing the parvocellular layers. Afferents to the PGn terminate in separate regions of this nucleus; the MT and adjacent visual cortices project into the internal layer of the PGn, whereas the polysensosy region of the STs projects into the external retinorecipient layer of the PGn. Possible functional implications of these projections are discussed.     

Neural coding of behavioral relevance in parietal cortex

Flexible control of behavior requires the selective processing of task-relevant sensory information and the appropriate linkage of sensory input to action. A great deal of evidence suggests a central role for the parietal cortex in these functions. Recent results from neurophysiological studies in non-human primates and neuroimaging experiments in humans illuminate the importance of parietal cortex for attention, and suggest how parietal neurons might allow the dynamic representation of behaviorally relevant information.     

Spatial and temporal coding in single neurons

Convergence between cells which differ in both spatial and temporal properties create higher order neurons with response properties that are distinctly different from those of the input neurons. The spatial properties of target neurons are not necessarily cosinetuned. In addition, unlike the independence between spatial and temporal properties in cosine-tuned afferent neurons, higher-order target cells generally exhibit a dependence of temporal dynamics on spatial properties. The response properties of target neurons receiving spatio-temporal convergence (STC) from tonic and phasic-tonic or phasic afferents is investigated here by considering a general case where the dynamic input is represented by a fractional, leaky, derivative transfer function. It is shown that, at frequencies below the corner frequency of the dynamic input, the temporal properties of target neurons can be described by leaky differentiators having time constants that are a function of spatial direction. Thus, STC target neurons exhibit tonic temporal response properties during stimulation along some spatial directions (having small time constants) and phasic properties along other directions (having large time constants). Specifically, target neurons encode the complete derivative of the stimulus along certain spatial directions. Thus, STC acts as a directionally specific high-pass filter and produces complete derivatives from fractional, leaky derivative afferent signals. In addition, spatio-temporal transformations can generate novel temporal dynamics in the central nervous system. These observations suggest that spatio-temporal computations might constitute an alternative to parallel, independent spatial and temporal channels.     

Correction of enophthalmos and superior sulcus depression in the anophthalmic orbit: a long-term follow-up

The purpose of this study was to review the long-term results in anophthalmic patients treated for enophthalmos. The patients in our series had augmentation of the volume of their orbital contents by subperiosteal placement of room-temperature vulcanized silicone. From 1972 to 1985, sixty-three patients received subperiosteal placement of room-temperature vulcanized silicone for their enophthalmos. Twenty-four of these patients were seen in long-term follow-up 1 to 13 years postoperatively. Indepth follow-up evaluation showed that room-temperature vulcanized silicone subperiosteal implantation for the treatment of enophthalmos and superior sulcus depression in the anophthalmic orbit is a reliable, safe procedure that is without serious complications and has excellent long-term results.     

A new visual area on the inferior wall of the cat cruciate sulcus

Properties of 187 neurons in the inferior wall of the cruciate sulcus, in an area where electrical stimulation evoked unidirectional saccadic eye movements, were investigated in waking cats. Of the total number 172 responded to visual stimulation. Neurons in the surface layers of the cortex responded to simple visual stimuli: light or dark spots or bars, both stationary and moving at speeds of around 30 deg/sec. These neurons showed no selectivity as regards stimulus orientation but sometimes behaved selectively toward the direction of their movements. In the intermediate layers the maximal neuronal response was obtained to a model of a bird flaping its wings. Neuronal responses in the depth of the cortex were characterized by selectivity to movement of stimuli toward or away from the animal in a certain part of the visual field, irrespective of whether a light stimulus was presented against a dark background or a dark stimulus against the light background. Responses to visual stimulation were exhibited only if the animal was in a state of activation, when the EEG showed desynchronization, and they were absent in a state of quite wakefulness. No responses were obtained to auditory or somatic stimulation. Responses to visual stimulation were not found in neurons of the medial wall of the brain beneath the cruciate sulcus, but responses were recorded to eye movements of definite size or orientation. It is postulated that at least two contiguous retinotopically organized zones exist in this part of the brain. Activity of one of them is connected with visual function, that of the other with eye movements.Institute for Problems in Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 16, No. 6, pp. 766–773, November–December, 1984.