Spatial Summation Research Articles

Neurosimilator for Undergraduate Biophysics and Neurophysiology Courses.

Stringent animal welfare principles are forcing undergraduate instructors to avoid the use of animals. Therefore, many hands-on lab sessions using laboratory animals are progressively replaced by computer simulations. These versatile software simulations permit the observation of the behavior of biological systems under a great variety of experimental conditions. While this versatility is important, computer simulations often work even when a student makes wrong assumptions, a situation that poses its own pedagogical problem. Hands-on learning provides pupils with the opportunity to safely make mistakes and learn organically through trial and error and should therefore still be promoted. We propose an electronic model of an excitable cell composed of different modules representing different parts of a neuron - dendrites, soma, axon and node of Ranvier. We describe a series of experiments that allow students to better understand differences between passive and active cell responses and differences between myelinated and demyelinated axons. These circuits can also be used to demonstrate temporal and spatial summation of signals coming to the neuron via dendrites, as well as the neuron coding by firing frequency. Finally, they permit experimental determination along with theoretical calculations of important biophysical properties of excitable cells, such as rheobase, chronaxie and space constant. This open-source model has been successfully integrated into an undergraduate course of the physiology of excitable cells and student feedback assessment reveals that it helped students to understand important notions of the course. Thus, this neuromorphic circuit could be a valuable tool for biophysics and neuroscience courses in other universities.

Rethinking simultaneous suppression in visual cortex via compressive spatiotemporal population receptive fields

When multiple visual stimuli are presented simultaneously in the receptive field, the neural response is suppressed compared to presenting the same stimuli sequentially. The prevailing hypothesis suggests that this suppression is due to competition among multiple stimuli for limited resources within receptive fields, governed by task demands. However, it is unknown how stimulus-driven computations may give rise to simultaneous suppression. Using fMRI, we find simultaneous suppression in single voxels, which varies with both stimulus size and timing, and progressively increases up the visual hierarchy. Using population receptive field (pRF) models, we find that compressive spatiotemporal summation rather than compressive spatial summation predicts simultaneous suppression, and that increased simultaneous suppression is linked to larger pRF sizes and stronger compressive nonlinearities. These results necessitate a rethinking of simultaneous suppression as the outcome of stimulus-driven compressive spatiotemporal computations within pRFs, and open new opportunities to study visual processing capacity across space and time.

Natural Organic Honey-CNT Memristor Based Artificial Synaptic Devices for Sustainable Neuromorphic System

Neuromorphic computing is considered to have the potential to overcome the limitations of traditional von Neumann architecture due to its high efficiency, low energy consumption, and fault-tolerance. Hardware components that can emulate the synaptic plasticity of neurons, i.e. artificial synaptic devices, are required by neuromorphic systems. New devices have been examined for such components, such as phase-change artificial synapse, ferroelectric artificial synapse, and memristor synapses. Among them, memristor, a two-terminal metal-insulator-metal structure that are analogous to a biological synapse with presynaptic neuron (top electrode), postsynapticneuron (bottom electrode), and synaptic cleft (memristive film), is a promising device technology because of its tunable resistance, scalability, 3D integration compatibility, low power consumption, and relatively high speed. In contrary to inorganic materials such as metal oxides, natural organic materials have attracted interest to form the memristive layer because they are renewable, biodegradable, sustainable, biocompatible, and environmentally friendly. In this paper, honey solution embedded with carbon nanotubes (CNTs) was processed into the memristive layer by a low cost solution-based process, with synaptic plasticity of the final honey-CNT memristors characterized, including forget and relearn, spike-rate-dependent plasticity, spike-voltage-dependent plasticity, short-term to long-term memory transition, paired pulse facilitation, and spatial supra-linear summation behaviors. The successful emulation of these essential biological synaptic behaviors demonstrates the potential of honey-CNT memristors as a viable hardware component in neuromorphic computing systems.

Retinal Ganglion Cell Content Underlying Standard Automated Perimetry Size I to V Visual Sensitivities in the Non-Human Primate Experimental Glaucoma Model.

To determine the relationship between visual sensitivities from white-on-white Goldmann size I to V stimuli and the underlying retinal ganglion cell (RGC) content in the non-human primate (NHP) experimental glaucoma model. Normative data were collected from 13 NHPs. Unilateral experimental glaucoma was induced in seven animals with the least variable fields who were monitored using optical coherence tomography and 30-2 full-threshold standard automated perimetry (SAP). At varying endpoints, animals were euthanized followed by perfusion fixation, and 1-mm retinal punches were obtained from 34 corresponding SAP locations. RGCs were immunolabeled with an antibody against an RNA-binding protein (RBPMS) marker and imaged using confocal microscopy. RGC counts from each location were then related to visual sensitivities for each stimulus size, after accounting for ocular magnification. At the endpoint, the circumpapillary retinal nerve fiber layer thickness for experimental glaucoma eyes ranged from 47 to 113µm. RGC density in control eyes was greatest for the 4.24° sample (18,024 ± 6869 cells/mm2) and decreased with eccentricity. Visual sensitivity at each tested location followed that predicted by spatial summation, with the critical area increasing with eccentricity (slope = 0.0036, R2 = 0.44). The relationship between RGC counts and visual sensitivity was described using a two-line fit, where the intercept of the first segment and hinge points were dependent on eccentricity. In NHPs, SAP visual thresholds are related to the underlying RGCs. The resulting spatial summation based structure-function model can be used to estimate RGC content from any standard white-on-white stimulus size.

Use of acoustic myography in evaluation of biceps brachii and triceps brachii muscle function in nine skijoring dogs

Abstract Studies have found pain and inflammation in the shoulder region of working sled dogs. As skijoring is a comparable, competitive winter sport, this act may result in injuries similar to those seen in sled dogs. The purpose of this study was to assess the duration of muscle contraction, temporal, and spatial summation (E-, S-, and T-scores) of the biceps and triceps brachii muscles and compare between skijoring and free-running. Nine skijoring dogs completed a free-run and skijoring trial on the same trail in random order. Acoustic myography (AMG), measuring on:off ratio (E-score), spatial summation (S-score), and temporal summation (T-score) of the biceps and triceps brachii was performed comparing the muscle work during skijoring and free-running tasks ensuring minimal acceleration during each recording period. Statistical analyses included Shapiro-Wilk tests, paired Student’s t-tests, two-way ANOVAs, and Mann-Whitney U tests. Significance was set at . When comparing the E-, S- and T-scores of the experienced dogs, the E-score of the triceps brachii was significantly lower during skijoring compared to free-running. When comparing the biceps versus the triceps in all dogs, T-score for the biceps was significantly lower than that of the triceps during skijoring. Males were significantly faster than the females during both the free-running and skijoring tasks. Males all fell in the experienced dog group. In experienced dogs, the increase in triceps workload during the task of skijoring with no apparent change in its antagonist, the biceps, could result in excess tension on the musculotendinous unit of the biceps. The relative workload of the biceps versus the triceps appears higher regarding temporal summation during skijoring.

Functional differences between the extraordinary eyes of deep-sea hyperiid amphipods.

The ocean's midwater is a uniquely challenging yet predictable and simple visual environment. The need to see without being seen in this dim, open habitat has led to extraordinary visual adaptations. To understand these adaptations, we compared the morphological and functional differences between the eyes of three hyperiid amphipods-Hyperia galba, Streetsia challengeri and Phronima sedentaria. Combining micro-CT data with computational modelling, we mapped visual field topography and predicted detection distances for visual targets viewed in different directions through mesopelagic depths. Hyperia's eyes provide a wide visual field optimized for spatial vision over short distances, while Phronima's and Streetsia's eyes have the potential to achieve greater sensitivity and longer detection distances using spatial summation. These improvements come at the cost of smaller visual fields, but this loss is compensated for by a second pair of eyes in Phronima and by behaviour in Streetsia. The need to improve sensitivity while minimizing visible eye size to maintain crypsis has likely driven the evolution of hyperiid eye diversity. Our results provide an integrative look at how these elusive animals have adapted to the unique visual challenges of the mesopelagic.

Low-voltage solution-processed NaxCu1−xI thin-film transistors for mimicking synaptic plasticity

In this article, NaxCu1−xI thin-film transistors gated by chitosan for low-voltage operation have been created by doping CuI with different Na concentrations (x = 0, 0.05, 0.1). It is found that the devices exhibit optimal performance when x is 0.05: a large current on/off ratio of 1.62 × 105, a steep subthreshold slope of 17.72 mV/dec, a saturation field-effect mobility of 0.51 cm2/V s, and a threshold voltage of 1.10 V. The operating voltage of the devices is reduced to below 2 V due to the electric-double-layer (EDL) effect. At a frequency of 10 Hz, a maximum specific capacitance of 1.36 μF/cm2 can be obtained in the chitosan. The effects of bias stress and laser on Na0.05Cu0.95I thin-film transistors (TFTs) have been examined at the end of the article, and the results revealed that Na0.05Cu0.95I TFTs possess good stability. As the bias stress gets longer and the laser power increases, the transfer curves of TFTs shift positively. Also, artificial synaptic behaviors and functions have been simulated experimentally. It can be divided into single-pulse, double-pulse, and multiple-pulse. According to the experimental results, features such as short-term plasticity, long-term plasticity, paired-pulse facilitation, high-pass filtering, pulse logic, and spatial summation have been achieved. The electrostatic modulation of EDL due to proton transverse migration is vital for this simulation. The realization of low-voltage synaptic Na0.05Cu0.95I TFTs prepared by solution method with pulse logic and spatial summation functions is crucial for application of portable biosensors and neuromorphic systems.

Visual Corticotectal Neurons in Awake Rabbits: Receptive Fields and Driving Monosynaptic Thalamocortical Inputs.

The superior colliculus receives powerful synaptic inputs from corticotectal neurons in the visual cortex. The function of these corticotectal neurons remains largely unknown due to a limited understanding of their response properties and connectivity. Here, we use antidromic methods to identify corticotectal neurons in awake male and female rabbits, and measure their axonal conduction times, thalamic inputs and receptive field properties. All corticotectal neurons responded to sinusoidal drifting gratings with a nonlinear (nonsinusoidal) increase in mean firing rate but showed pronounced differences in their ON-OFF receptive field structures that we classified into three groups, Cx, S2, and S1. Cx receptive fields had highly overlapping ON and OFF subfields as classical complex cells, S2 had largely separated ON and OFF subfields as classical simple cells, and S1 had a single ON or OFF subfield. Thus, all corticotectal neurons are homogeneous in their nonlinear spatial summation but very heterogeneous in their spatial integration of ON and OFF inputs. The Cx type had the fastest conducting axons, the highest spontaneous activity, and the strongest and fastest visual responses. The S2 type had the highest orientation selectivity, and the S1 type had the slowest conducting axons. Moreover, our cross-correlation analyses found that a subpopulation of corticotectal neurons with very fast conducting axons and high spontaneous firing rates (largely "Cx" type) receives monosynaptic input from retinotopically aligned thalamic neurons. This previously unrecognized fast-conducting thalamic-mediated corticotectal pathway may provide specialized information to superior colliculus and prime recipient neurons for subsequent corticotectal or retinal synaptic input.

Exercise-induced potentiation of the acute hypoxic ventilatory response: Neural mechanisms and implications for cerebral blood flow.

A given dose of hypoxia causes a greater increase in pulmonary ventilation during physical exercise than during rest, representing an exercise-induced potentiation of the acute hypoxic ventilatory response (HVR). This phenomenon occurs independently from hypoxic blood entering the contracting skeletal muscle circulation or metabolic byproducts leaving skeletal muscles, supporting the contention that neural mechanisms per se can mediate the HVR when humoral mechanisms are not at play. However, multiple neural mechanisms might be interacting intricately. First, we discuss the neural mechanisms involved in the ventilatory response to hypoxic exercise and their potential interactions. Current evidence does not support an interaction between the carotid chemoreflex and central command. In contrast, findings from some studies support synergistic interactions between the carotid chemoreflex and the muscle mechano- and metaboreflexes. Second, we propose hypotheses about potential mechanisms underlying neural interactions, including spatial and temporal summation of afferent signals into the medulla, short-term potentiation and sympathetically induced activation of the carotid chemoreceptors. Lastly, we ponder how exercise-induced potentiation of the HVR results in hyperventilation-induced hypocapnia, which influences cerebral blood flow regulation, with multifaceted potential consequences, including deleterious (increased central fatigue and impaired cognitive performance), inert (unchanged exercise) and beneficial effects (protection against excessive cerebral perfusion).

Spatial summation of pain is associated with pain expectations: Results from a home-based paradigm.

The purpose of this study was to reproduce the previously observed spatial summation of pain effect (SSp) using non-laboratory procedures and commercial equipment. An additional aim was to explore the association between expectations and SSp. The Cold Pressor Task (CPT) was used to induce SSp. Healthy participants (N = 68) immersed their non-dominant hands (divided into 5 segments) into cold water (CPT). Two conditions were used 1) gradual hand immersion (ascending condition) and 2) gradual hand withdrawal (descending condition). Pain intensity was measured on a Visual Analogue Scale (VAS). Psychological factors, such as the participants' expectations of pain intensity were also measured on a VAS. Results showed significant SSp (χ2(4) = 116.90, p < 0.001), reproduced with non-laboratory equipment in a home-based set-up. Furthermore, two novel findings were observed: i) there was a significant correlation between expectations and perceived pain, indicating a link between pain expectations and SSp, ii) spatial summation increased with the increase in duration exposure to the noxious stimulus (Wald χ2(8) = 80.80, p < 0.001). This study suggests that SSp is associated with pain expectations and can be formed by a mixture of excitatory and inhibitory mechanisms potentially driven by temporal characteristics of neural excitation. Moreover, this study proposes a new feasible way to induce SSp using a home-based set-up.

Perception Threshold for Pressure by a Soft Textile Actuator.

Electroactive textile (EAT) has the potential to apply pressure stimuli to the skin, e.g. in the form of a squeeze on the arm. To present a perceivable haptic sensation we need to know the perception threshold for such stimuli. We designed a set-up based on motorized ribbons around the arm with five different widths (range 3 - 49 mm) for psychophysical studies. We investigated the perception threshold of force pressure and ribbon reduction in two studies, using two methods (PSI and 1up/3down staircase), comparing sex, the left and right arm, the lower and upper arm, and stimulated surface area with a total of 57 participants. We found that larger stimulation surfaces require less pressure to reach the perception threshold (0.151 N per cm 2 for 3 mm width, 0.00972 N per cm 2 for 49 mm width on the lower arm). This indicates a spatial summation effect for these pressure stimuli. We did not find significant differences in perception threshold for the left and right arm and, the upper and lower arm. Between male and female participants we found significant differences for two conditions (10 mm and 25 mm) in Experiment 1, but we could not reproduce this in Experiment 2.

Morphological disruption and visual tuning alterations in the primary visual cortex in glaucoma (DBA/2J) mice.

Glaucoma is a leading cause of irreversible blindness worldwide, and previous studies have shown that, in addition to affecting the eyes, it also causes abnormalities in the brain. However, it is not yet clear how the primary visual cortex (V1) is altered in glaucoma. This study used DBA/2J mice as a model for spontaneous secondary glaucoma. The aim of the study was to compare the electrophysiological and histomorphological characteristics of neurons in the V1 between 9-month-old DBA/2J mice and age-matched C57BL/6J mice. We conducted single-unit recordings in the V1 of light-anesthetized mice to measure the visually induced responses, including single-unit spiking and gamma band oscillations. The morphology of layer II/III neurons was determined by neuronal nuclear antigen staining and Nissl staining of brain tissue sections. Eighty-seven neurons from eight DBA/2J mice and eighty-one neurons from eight C57BL/6J mice were examined. Compared with the C57BL/6J group, V1 neurons in the DBA/2J group exhibited weaker visual tuning and impaired spatial summation. Moreover, fewer neurons were observed in the V1 of DBA/2J mice compared with C57BL/6J mice. These findings suggest that DBA/2J mice have fewer neurons in the V1 compared with C57BL/6J mice, and that these neurons have impaired visual tuning. Our findings provide a better understanding of the pathological changes that occur in V1 neuron function and morphology in the DBA/2J mouse model. This study might offer some innovative perspectives regarding the treatment of glaucoma.

Multichannel Vibrotactile Glove: Validation of a new device designed to sense vibrations.

There is a growing interest in using the tactile modality as a compensation or sensory augmentation tool in various fields. The Multichannel Vibrotactile Glove was designed to meet the needs of these diverse disciplines and overcome the limitations of current sound-to-touch technologies. Using 12 independent haptic exciters on each finger's back and on the palm, the device can convey acoustic information to cutaneous vibrotactile receptors with precise control of the location, frequency, timing, and intensity. A staircase method was used to model vibration detection thresholds at six frequencies (100, 200, 250, 500, 800, 1000 Hertz) for each actuator position (All, Thumb, Index, Major, Middle, Pinky, Palm) and both hands (Right, Left). No between hand difference was observed and all finger actuators provided consistent thresholds, except for the Palm which exhibited higher thresholds. Spatial summation effects were observed when all actuators were activated simultaneously. Detection thresholds significantly increased at 100 Hertz and above 500 Hertz. These findings confirm that the system provides uniform stimulation across hands and actuators. Overall, the Multichannel Vibrotactile Glove provides the freedom to send various acoustic features to individual actuators, providing a versatile tool for research and a potential technology to substitute, compensate, or extend sensory perception.

Investigating the Spatiotemporal Summation of Perimetric Stimuli in Dry Age-Related Macular Degeneration.

To measure achromatic spatial, temporal, and spatiotemporal summation in dry age-related macular degeneration (AMD) compared to healthy controls under conditions of photopic gaze-contingent perimetry. Twenty participants with dry AMD (mean age, 74.6 years) and 20 healthy controls (mean age, 67.8 years) performed custom, gaze-contingent perimetry tests. An area-modulation test generated localized estimates of Ricco's area (RA) at 2.5° and 5° eccentricities along the 0°, 90°, 180°, and 270° meridians. Contrast thresholds were measured at the same test locations for stimuli of six durations (3.7-190.4 ms) with a Goldmann III stimulus (GIII, 0.43°) and RA-scaled stimuli. The upper limit (critical duration) of complete temporal summation (using the GIII stimulus) and spatiotemporal summation (using the RA stimuli) was estimated using iterative two-phase regression analysis. Median (interquartile range [IQR]) RA estimates were significantly larger in AMD participants (2.5°: 0.21 [0.09-0.41] deg2; 5°: 0.32 [0.15-0.65 deg2]) compared to healthy controls (2.5°: 0.08 [0.05-0.13] deg2; 5°: 0.15 [0.08-0.22] deg2) at all test locations (all P < 0.05). No significant difference in median critical duration was found in AMD participants with the GIII stimulus (19.6 [9.9-30.4] ms) and RA-scaled stimuli (22.9 [13.9-40.3] ms) compared to healthy controls (GIII: 17.0 [11.3-24.0] ms; RA-scaled: 22.4 [14.3-33.1] ms) at all test locations (all P > 0.05). Spatial summation is altered in dry AMD, without commensurate changes in temporal summation. The sensitivity of perimetry to AMD may be improved by utilizing stimuli that probe alterations in spatial summation in the disease.

Effects of virtual reality on psychophysical measures of pain: superiority to imagination and nonimmersive conditions.

Virtual reality (VR) has been shown to be effective in pain management. However, to date, little is known about the mechanisms by which immersive experiences influence pain processing. The aim of this study was to investigate the direct effects of an immersive VR environment on the perception of experimental pain in individuals with chronic pain and pain-free controls. The immersion in a VR landscape was compared with mental imagery and a nonimmersive control condition. Using a randomized within-crossover design, pressure pain detection and tolerance thresholds, spatial and temporal summation (SSP, TSP), and conditioned pain modulation (CPM) were measured in 28 individuals with chronic pain and 31 pain-free controls using phasic cuff pressure on the legs. Direct comparison between the groups showed that although individuals with pain had significantly lower pain thresholds, reduced CPM effects, and increased TSP, the VR condition had the same pain-inhibitory effect on pain thresholds as in pain-free controls. Conditioned pain modulation effects were reduced by all conditions compared with baseline. There were no significant differences between conditions and baseline for TSP and SSP. Overall, pain modulatory effects were largest for VR and smallest for imagery. These results demonstrate that immersion in a VR environment has an increasing effect on pain thresholds, reduces pain inhibition in a CPM paradigm, and has no effects on TSP. This applies for participants with chronic pain and pain-free controls. These VR effects exceeded the effects of mental imagery on the nonimmersive control condition. This indicates that VR effectively modulates pain perception in both patients and controls irrespective of differences in pain perception.

The Use of Induction Sensors and Helmet-Based Shielding Technology to Identify Differences in Electromagnetic Fields in Patients With Cranial Neurological Disease Versus Healthy Controls.

Background and objective Electromagnetic fields (EMFs) stemming from neural circuits have been evaluated in healthy human subjects by using non-invasive induction sensor technologies with adjunctive shielding constrained to a helmet constructed of Mu-metal and copper mesh. These EMF measurements have been analyzed and discerned to alterphysiological states of movement, thoughts of movement, emotional thoughts, andplanned activities. However, these technologies have not yet been investigated as a diagnostic tool in patients with cranial neurological pathology to evaluate differences in patterns in the pathologic state compared to healthy controls. In light of this, we conducted this study to address this scarcity of data. Methods An observational study was conducted in which patients at a single center with cranial neurological disease of all causes were eligible to enroll; they had real-time non-invasive continuous EMF measurements obtained using induction sensors and a shielded helmet. These measurements were obtained in the resting state and then compared to previously obtained measurements in healthy volunteers. Post-processing analysis was conducted to evaluate the derivatives of these EMFs to identify changes in patterns. Results Fourteen patients with traumatic injury, stroke, and neoplasm with ages ranging from 14 to 81 years underwent successful analysis and post-processing of their cortically generated EMF waves. Patterns of EMF waves were compared topreviously obtained data from four healthy controls. It was identified that there was less variation in the EMF measurements in patients with neurological disease compared to healthy controls. This was identified based on differences in derivatives of the EMF waves anddecreased numbers of peaks and valleys in the EMF waves. Conclusions Novel induction sensors with an engineered, layered Mu-metal and copper mesh helmet for shielding with Mu-metal EMF channels appear to be efficient in measuring neural circuit-driven EMF non-invasively, in real-time, and continuously and can discern differences in EMF patterns between healthy volunteers and patients with neural circuit pathology. The decreased variability in EMF measurements in patients with neural pathology and greater decreases in slope within low-frequency measurements may be correlated with disrupted neural signaling from dysfunctional neurons and abnormalities in spatial and temporal summation. Some EMF changes inill individuals correspond to changes in the experimentally induced lesions in the animal model. Further studies are warranted to devise models of disease and healthy states to improve these technologies as a diagnostic modality.

Elucidating the relationship between spatial summation and center-surround antagonism

Elucidating the relationship between spatial summation and center-surround antagonism

Spatial summation for motion detection

Spatial summation for motion detection

Suprathreshold length summation.

To investigate the mechanisms underlying elongated spatial summation with a pattern-masking paradigm, we measured the contrast detection thresholds for elongated Gabor targets situated at 3° eccentricity to either the left or right of the fixation and elongated along an arc of the same radius to access homogeneous retinal sensitivity. The mask was a ring with a Gabor envelope of the same 3° center radius containing either a concentric (iso-orientation mask) or a radial (orthogonal mask) modulation. The task of the observer was to indicate whether the target in each trial was on the left or the right of the fixation. With orthogonal or low contrast iso-orientation masks, target thresholds first decreased with size with slope -1 on log-log coordinates until the target length reached 45' (specified as the half-height full-width of the Gabor envelope) and then further decreased according to a slope of -1/2, the latter being the signature of an ideal summation process. When the contrast of the iso-orientation mask was sufficiently high, however, the target thresholds, while still showing a -1 slope up to ∼10', asymptoted up to about 50' length, suggesting that the presence of the mask eliminated the ideal summation regime. Beyond about 50', the data approximated another -1 slope decrease in threshold, suggesting the existence of an extra-long channel that is not revealed by the conventional spatial summation paradigm. The full results could be explained by a divisive inhibition model, in which second-order filters sum responses across local oriented channels, combined with a single extra-long filter at least 300' in extent. In this model, the local filter response is given by the linear excitation of the local channels raised to a power, and scaled by divisive inhibition from all channels in the neighborhood. With the high-contrast iso-orientation masks, such divisive inhibition swamps the response to eliminate the ideal summation regime until the stimulus is long enough to activate the extra-long filter.

Cutaneous warmth and hotness thresholds to radiation heat exposure at a distance of 10 cm from 17 body regions

The purpose of the present study was to evaluate body regional differences in cutaneous warmth and hotness thresholds in relation to radiant heat exposure. Fourteen male subjects participated in this study (age: 25 ± 5 y, height: 176.6 ± 5.5 cm, body weight: 70 ± 5.8 kg). Cutaneous warmth and hotness thresholds were measured on the forehead, neck, chest, abdomen, upper back, lower back, upper arm, forearm, palm, back of hand, front thigh, shin, top of foot, buttock, back thigh, calf, and sole. The forehead (34.8 ± 0.2 °C), lower back (34.1 ± 1.2 °C) and palm (34.3 ± 0.7 °C) had the highest warmth thresholds, whereas the foot (29.8 ± 1.9 °C) and sole (28.0 ± 2.1 °C) had the lowest values among the 17 regions (P<0.001). Higher warmth thresholds were related to higher initial skin temperatures (Tsk) (r=0.972, P<0.001). Increases in Tsk for detecting warmth sensation were smaller for the lower back with a rise of 0.2 ± 0.4 °C and the abdomen (0.3 ± 0.3 °C) than for the buttock (0.9 ± 0.8 °C) and sole (0.8 ± 0.6 °C) (P<0.05). Increases in Tsk for detecting hotness sensation ranged from 0.5 to 1.5 °C. Warmth and hotness thresholds on the abdomen or sole had significant relationships with body mass index, indicating that the overweight are less sensitive to detecting radiant heat on the abdomen or sole. Thermal thresholds from radiant heat exposure of 100 cm2 were lower than the values from conductive heat exposure of 6.25 cm2, which might be explained by the effect of spatial summation.