Functional Architecture of Eye Position Gain Fields in Visual Association  Cortex of Behaving Monkey

Siegel, Ralph M.; Raffi, Milena; Phinney, Raymond E.; Turner, Jessica A.; Jandó, Gábor

doi:10.1152/jn.01179.2002

Cited by 42 publications

(86 citation statements)

References 33 publications

(53 reference statements)

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“…Optical imaging of changes in the oxygenation of hemoglobin within and across the cortical surface permits the evaluation of global neuronal network activity (Malonek and Grinvald, 1996). Area 7a and the dorsal prelunate (DP) area, two gyral portions of the inferior parietal lobule, are accessible to direct visualization for intrinsic optical imaging (Siegel et al, 2003). Area 7a, which lies close to the intraparietal sulcus, is modulated by the inferior, contralateral position of the eye in the orbit.…”

Section: Introductionmentioning

confidence: 99%

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Functional Architecture of Spatial Attention in the Parietal Cortex of the Behaving Monkey

Raffi¹,

Siegel²

2005

J. Neurosci.

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Functional architectures facilitate orderly transmittal of representations between cortices, allow for local interactions between neurons, and ensure a uniform distribution of feature representations with respect to larger-scale topographies. We sought to correlate such topographies with internal cognitive states. A psychophysical task for which the monkey was required to detect a change in one of two identical peripheral expanding flow fields tested for spatial shifts of attention. The monkey was cued as to which flow would change with a small cue near the fixation points. Reaction time data indicate that the monkey's performance in the optic flow detection task depended on the location of the cue. Using optical imaging of intrinsic signals, we show that a monkey's internally generated locus of attention is correlated with an 800 -860 m patchy topological architecture across the cortical surface of the inferior parietal lobule. The attentional patches vary in location but are stable in spatial frequency. The patches are embedded in a larger-scale and stable representation of eye position. Trial-by-trial analysis of the images indicates that the organizational scheme with simultaneous stable and variable subcomponents occurs within the experiment of 1 d, as well as across days. This novel functional architecture is the first to be correlated with attentional mechanisms and could support a fine-scale functional architecture underlying hemispatial neglect, an attentional deficit caused by parietal lesions.

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Section: Introductionmentioning

confidence: 99%

“…The neighboring DP represents the superior, contralateral eye position. A push-pull relationship between these two areas suggests that they may have a distributed representation of the position of the eye (Siegel et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

Functional Architecture of Spatial Attention in the Parietal Cortex of the Behaving Monkey

Raffi¹,

Siegel²

2005

J. Neurosci.

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“…The ISOI studies also suggested that the rebound was more spatially diffuse and less stimulus-specific than the initial dip (4,7,10). The initial dip thus became the signal of choice in a number of functional imaging studies, not only in ISOI (11)(12)(13)(14)(15) but also in fMRI (16).…”

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confidence: 98%

Spatiotemporal precision and hemodynamic mechanism of optical point spreads in alert primates

Sirotin

Hillman

Bordier

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

116

144

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In functional brain imaging there is controversy over which hemodynamic signal best represents neural activity. Intrinsic signal optical imaging (ISOI) suggests that the best signal is the early darkening observed at wavelengths absorbed preferentially by deoxyhemoglobin (HbR). It is assumed that this darkening or "initial dip" reports local conversion of oxyhemoglobin (HbO) to HbR, i.e., oxygen consumption caused by local neural activity, thus giving the most specific measure of such activity. The blood volume signal, by contrast, is believed to be more delayed and less specific. Here, we used multiwavelength ISOI to simultaneously map oxygenation and blood volume [i.e., total hemoglobin (HbT)] in primary visual cortex (V1) of the alert macaque. We found that the hemodynamic ''point spread,'' i.e., impulse response to a minimal visual stimulus, was as rapid and retinotopically specific when imaged by using blood volume as when using the initial dip. Quantitative separation of the imaged signal into HbR, HbO, and HbT showed, moreover, that the initial dip was dominated by a fast local increase in HbT, with no increase in HbR. We found only a delayed HbR decrease that was broader in retinotopic spread than HbO or HbT. Further, we show that the multiphasic time course of typical ISOI signals and the strength of the initial dip may reflect the temporal interplay of monophasic HbO, HbR, and HbT signals. Characterizing the hemodynamic response is important for understanding neurovascular coupling and elucidating the physiological basis of imaging techniques such as fMRI.fMRI ͉ imaging ͉ macaque ͉ visual ͉ neurovascular coupling C erebral hemodynamics respond quickly and specifically to local neural activity (1, 2). Hemodynamic signals are thus used extensively as proxies for such activity in functional neuroimaging techniques like fMRI and intrinsic signal optical imaging (ISOI). There has been considerable debate, however, as to which of the possible hemodynamic signals, e.g., changes in local blood oxygenation, volume, or flow, with their distinct response properties, constitutes the ''best'' signal for inferring neural activity (1,(3)(4)(5).The debate regarding the best signal sharpened with reports of initial dips in both ISOI and fMRI signals. ISOI studies consistently found a brief stimulus-evoked darkening followed by a strong brightening at imaging wavelengths preferentially absorbed in deoxyhemoglobin (HbR) [e.g., at 605 nm (6)]. The darkening, later termed the initial dip*, was interpreted as a local conversion of oxyhemoglobin (HbO) to HbR caused by increased oxygen consumption by local neurons before any active vascular response (1, 7) The subsequent brightening was taken to measure the ''rebound'' in [HbO] † caused by a delayed, stimulus-triggered increase in cerebral blood flow (7).In parallel, some fMRI studies reported finding an initial dip before the rise in the blood oxygen level-dependent (BOLD) signal (8). Because the BOLD signal measures changes in [HbR] alone ‡ , the fMRI initial dip was seen a...

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“…This has not yet been systematically attempted. However, in parietal areas 7a and DP, Siegel and coworkers have used a peripheral detection task to uncover topographic representations of the contralateral hemifield with intrinsic optical imaging (22)(23)(24).In this study, we mapped the functional and topographic organization of macaque LIP using BOLD fMRI in two macaques performing a demanding rapid serial visual presentation (RSVP) search task. The task does not address the relative roles of LIP in oculomotor planning and the allocation of spatial attention.…”

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confidence: 99%

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confidence: 99%

Topographic organization of macaque area LIP

Patel

Shulman

Baker

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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Despite several attempts to define retinotopic maps in the macaque lateral intraparietal area (LIP) using histological, electrophysiological, and neuroimaging methods, the degree to which this area is topographically organized remains controversial. We recorded blood oxygenation level-dependent signals with functional MRI from two macaques performing a difficult visual search task on stimuli presented at the fovea or in the periphery of the visual field. The results revealed the presence of a single topographic representation of the contralateral hemifield in the ventral subdivision of the LIP (LIPv) in both hemispheres of both monkeys. Also, a foveal representation was localized in rostral LIPv rather than in dorsal LIP (LIPd) as previous experiments had suggested. Finally, both LIPd and LIPv responded only to contralateral stimuli. In contrast, human studies have reported multiple topographic maps in intraparietal cortex and robust responses to ipsilateral stimuli. These blood oxygenation level-dependent functional MRI results provide clear evidence for the topographic organization of macaque LIP that complements the results of previous electrophysiology studies, and also reveal some unexpected characteristics of this organization that have eluded these previous studies. The results also delineate organizational differences between LIPv and LIPd, providing support for these two histologically defined areas may subserve different visuospatial functions. Finally, these findings point to potential evolutionary differences in functional organization with human posterior parietal cortex.T he macaque lateral intraparietal area (LIP) has been the subject of many investigations over the past few decades. Anatomical studies of this area, which lies on the lateral bank of the intraparietal sulcus (IPS), have demonstrated widespread connectivity with a variety of cortical areas (1-3). Electrophysiological recordings in awake behaving macaques indicate that these connections underlie LIP's role in a range of functions ranging from the planning of saccades to the allocation of attention to the valuation of sensory information (4-6).Despite the many studies of its functional and anatomical properties, the topographic organization of LIP remains controversial. Two electrophysiology studies have reported that LIP has a strong contralateral bias and may be retinotopically organized (3, 7). However, the maps in these studies were coarse and not consistent with one another. In contrast, another study found neither a retinotopic map nor a contralateral-hemifield bias (8). Electrical stimulation studies of LIP have also resulted in an unusual result: in both studies, the sites representing the horizontal meridian lie rostral to those representing both the lower and upper visual fields (9, 10). Thus, the issue of topography in LIP remains an open question.Architectonic studies have divided LIP into dorsal and ventral divisions, but the functional significance of this difference is unclear (3, 11). Although cells throughout LIP appe...

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Functional Architecture of Eye Position Gain Fields in Visual Association Cortex of Behaving Monkey

Cited by 42 publications

References 33 publications

Functional Architecture of Spatial Attention in the Parietal Cortex of the Behaving Monkey

Functional Architecture of Spatial Attention in the Parietal Cortex of the Behaving Monkey

Spatiotemporal precision and hemodynamic mechanism of optical point spreads in alert primates

Topographic organization of macaque area LIP

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