Bilateral hemodynamic optical imaging reveals a decrease in ipsilateral blood oxygenation and flow
(A) HbO, Hb, HbT and speckle contrast images following stimulus onset (t=0). The color scale is expressed as percent signal change relative to pre-stimulus baseline (ΔC/C₀). Time (in seconds) relative to stimulus onset is indicated above the images. 150 trials were averaged. We assumed baseline concentrations of 60 μM and 40 μM for HbO and Hb, respectively. An image of raw vasculature corresponding to functional frames is shown in the upper left corner. Contra: contralateral to the stimulus hemisphere, ipsi: ipsilateral to the stimulus hemisphere.
(B) Top: Signal time-courses extracted from the contralateral (solid lines) and ipsilateral (dashed lines) hemispheres for HbO (red), Hb (blue) and HbT (green). Bottom: The same for speckle contrast. Note that a decrease in speckle contrast indicated an increase in blood flow.
(C) HbO as in (B) broken into the center (within a 1.5-mm ring around the center of the response, solid red) and the surround (outside the 1.5-mm ring, dashed red). The center was estimated using the earliest HbT response. Contra: contralateral to the stimulus hemisphere; ipsi: ipsilateral to the stimulus hemisphere.
(D)Bar graphs of ΔHbO, ΔHb, ΔHbT and Δspeckle contrast quantifying the biphasic ipsilateral response. For each measure the 1^st bar represents the initial (small) oxygenation/flow increase, and the 2^nd bar represents the consecutive (big) oxygenation/flow decrease. Data from 5 subjects were averaged. The error bars indicate standard error across subjects. The following are ipsilateral mean±SE, peaks reported in their temporal order: HbO, 0.11±0.03, -0.75±0.22; Hb -0.07±0.02, 0.56±0.2; HbT, 0.07±0.02, -0.26±0.07; speckle contrast, -0.28±0.01, 1.3±0.2.

Arteriolar diameter change in response to contra- and ipsilateral stimulation
White traces show percent diameter change relative to the baseline (Δd/d) at different locations indicated by arrows. At every location the upper and lower trace in a pair represents the response to the contra- and ipsilateral stimulation, respectively. Dilation is plotted upward; constriction, downward. The center of the neuronal response was mapped on the cortical surface using a ball electrode. Surface potential recordings from different locations are shown in red. The strongest amplitude and fastest rise time indicate the center. The traces are overlaid on a 2-photon image of vasculature within the exposure. The image was calculated as a maximum intensity projection of an image stack 0-300 μm in depth. Individual images were acquired every 10 μm. The horizontal dimension is 3.2 mm.

Comparison of arteriolar dilatation and constriction in response to contra- and ipsilateral stimulation
(A) An average of arteriolar diameter changes (Δd/d) in response to contralateral stimulation (blue) and ipsilateral stimulation (red). All measured vessels from all subjects are averaged. Dilation and constriction are plotted upward and downward, respectively.
B) Peak dilation (crosses) and peak constriction (circles) as a function of distance (in mm from the center of evoked neuronal response) in response to contralateral stimulation (top panel) and ipsilateral stimulation (bottom panel). Each dot represents a measurement from a single arteriole. Data from 7 subjects are superimposed.

Comparison of surface and diving arterioles
(A) Diameter changes (Δd/d) in response to contralateral stimulation (blue) and ipsilateral stimulation (red) at 4 locations were measured in one subject. At every location the measurement was made from a parent surface arteriole (s, top pair of traces) and a penetrating (diving) arteriole (p, bottom pair of traces). Dilation and constriction are plotted upward and downward, respectively. Black arrows indicate stimulus onset. Red arrows point to the specific surface arterioles from which the measurements were made. The red circle shows the center of neuronal response. Depth (in μm) is indicated next to each penetrating arteriole. The image of the vasculature was calculated as a maximum intensity projection of an image stack 0-300 μm in depth. Individual images were acquired every 10 μm.
(B)Peak ipsilateral constriction of diving arterioles as a function of that of a parent surface branch. Amplitude was normalized using dilation in response to the contralateral stimulation. Data from 3 subjects are superimposed.
(C)Depth distribution of the measured diving arterioles.

2DG-autoradiography in response to a unilateral stimulation
(A) Sector map used for quantitative analysis is overlaid on a coronal brain section. The color scale is expressed in units of local cerebral metabolic rate of glucose, LCMRglu (μmol/100g/min).
(B) Cortical glucose utilization profile as a function of sector number. The direction is from close to the medial ridge (sector 1) to the most lateral point of the hemisphere where the horizontal dimension of the brain is the widest (sector 20). Profiles from the contralateral (blue) and ipsilateral (red) hemispheres, posterior to the active area (green), and control subjects (no stimulus, black) are superimposed. The profiles extracted from each section have been normalized to the mean section intensity before averaging. Y-axis is expressed as % change relative to mean section intensity. Data points statistically significant from the control (p<0.05) are indicated by stars.
(C) Raw (not normalized) profiles extracted from the contralateral hemisphere (blue), the ipsilateral hemisphere (red), posterior to the active area (green), and control subjects (no stimulus, black). Each line represents one hemisphere. Subjects are superimposed on each plot.

Laminar distribution of glucose uptake
A cortical glucose utilization profile is shown as a function of sector number in the contralateral hemisphere (left column, blue) and the ipsilateral hemisphere (right column, red). The depth axis of the sector map was divided into 4 slabs. Each one of the plots shows the profiles extracted from one of the slabs schematically shown in the upper left corner. Each data point within a profile was calculated by averaging pixels within each of the sectors in the corresponding slab. Profiles are superimposed onto the baseline at the same depth estimated from the region posterior to the active area (black). The direction of x-axis is as in Fig. 5: from close to the medial ridge (sector 1) to the most lateral point of the hemisphere where the horizontal dimension of the brain is the widest (sector 20). The profiles extracted from each section have been normalized to the mean section intensity before averaging. Y-axis is expressed as % change relative to mean section intensity. Data points statistically significant from the control (p<0.05) are indicated by stars.

Laminar recordings of multiunit activity measure an increase in ipsilateral spiking
(A)A laminar profile of MUA response in the contralateral (left panel) and ipsilateral (right panel) hemispheres. The response to the first of the 6 stimuli in a train is shown. Each trace represents a recording from a single electrode in the array. The corresponding cortical depth is indicated on the left. Recordings from every other contact down to 2000 μm are shown. 500 stimulation trials were averaged. Arrows denote stimulus onset. Note an increase in ipsilateral spiking.
(B)MUA from supragranular (above 500 μm, red), granular (500-900 μm, green) and infragranular (below 900 μm, blue) layers. Black arrows indicate response onset.
(C)Infragranular MUA responses from 4 subjects are superimposed.