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O Creutzfeldt

Publications and source records attributed to O Creutzfeldt.

At least 19 recordsLinked to original sources
PubMed1990

Chromatic induction and brightness contrast: a relativistic color model.

It has been suggested that object colors in a colored environment are the result of combining in perception the (relative) brightness of each spectral component rather than of just mixing the spectral luminances. We tested this hypothesis with the following experiment: A pair of center-surround targets made of colored papers was illuminated with trichromatic white light. Two identical central color plates (test and match field, respectively) were surrounded by frames of different colors and thus looked different because of simultaneous color contrast. Observers were asked to match the colors by changing the illumination of the match field by means of a color-mixture projector (color match, CM). This color-matched reflectance was measured with a photometer, and its CIE coordinates were determined. We then illuminated the display with one of the three primaries that made up our trichromatic white light. The different reflectances of the different surrounds at each primary induced simultaneous brightness contrast. The brightnesses of the two central plates were therefore different. Observers were asked to change the intensity of the illumination of the match field at the respective primary so that it looked equally bright as the test field. This procedure was repeated for each primary (primary brightness match, PBM). Then the whole display except for the match field was illuminated with the trichromatic white as before, while the latter was illuminated with a trichromatic mixture consisting of the primaries at the intensities as set in the PBM experiment, and the CIE values were determined with the photometer. The CIE values of the match field after the CM and PBM procedures were nearly identical. This indicates that composite colors are composed in perception by combining the scaled (or relative) brightness of each spectral component and that this brightness scaling is largely restricted to interactions in the same spectral region. The results are compared with those of other models concerned with contrast colors as well as with neurophysiological data. Some limitations are mentioned.

Adult↗
PubMed1989

Neuronal activity in the human lateral temporal lobe. I. Responses to speech.

Single and multiple unit neuronal activity was recorded from the cortex of the lateral temporal lobe in conscious humans during open brain surgery for the treatment of epilepsy. Recordings were obtained from the right and left superior, middle and inferior temporal gyrus of 34 patients (41 recording sites). Recordings were restricted to regions to be resected during subsequent surgery. This excluded recordings from language areas proper. Neuronal responses to words and sentences presented over a loudspeaker and during free conversation were recorded. No significant differences between the right and left hemisphere were obvious. All neurons in the superior temporal gyrus responded to various aspects of spoken language with temporally well defined activation/inhibition patterns, but not or only little to non-linguistic noises or tones. Excitatory responses were typically short or prolonged (up to several hundred ms) bursts of discharges at rates above 20/sec, reaching peak rates of 50-100/s. Such responses could be specifically related to certain combinations of consonants suggesting a function in categorization, they could depend on word length, could differentiate between polysyllabic and compound words of the same length or could be unspecifically related to language as such. No formant specific responses were found, but the prolonged excitations across syllables suggest that consonant/vowel combinations may play a role for some activation patterns. Responses of some neurons (or neuronal populations) depended on the attention paid to the words and sentences, or the task connected with them (repeat words, speech addressed to the patient demanding something). Neurons in the middle and inferior temporal gyrus were only little affected by listening to single words or sentences, but some were unspecifically activated by words or while listening to sentences. Excitatory responses varied within a limited range of discharge rates usually below 5-10/s. Phonetic distortion of spoken language could reduce responses in superior temporal gyrus neurons, but also the slight changes in discharge rate of middle temporal neurons could be absent during distorted and uncomprehensible speech sounds. We conclude that superior temporal gyrus neuron responses reflect some general phonetic but not semantic aspects of spoken language. Middle and inferior temporal gyrus neurons do not signal phonetic aspects of language, but may be involved in understanding language under certain conditions.

Epilepsy↗
PubMed1989

Neuronal activity in the human lateral temporal lobe. II. Responses to the subjects own voice.

We have recorded neuronal responses in the lateral temporal lobe of man to overt speech during open brain surgery for epilepsy. Tests included overt naming of objects and reading words or short sentences shown on a projector screen, repetition of tape recorded words or sentences presented over a loudspeaker, and free conversation. Neuronal activity in the dominant and non-dominant temporal lobe were about equally affected by overt speech. As during listening to language (see Creutzfeldt et al. 1989), responses differed between recordings from sites in the superior and the middle or inferior temporal gyrus. In the superior temporal gyrus all neurons responded clearly and each in a characteristic manner. Activation could be related to phonemic aspects, to segmentation or to the length of spoken words or sentences. However, neurons were mostly differently affected by listening to words and language as compared to overt speaking. In neuronal populations recorded simultaneously with one or two microelectrodes, some neurons responded predominantly to one or the other type of speech. Excitatory responses during overt speaking were always auditory. In the middle temporal gyrus more neurons (about 2/3) responded to overt speaking than to listening alone. Activations elicited during overt speech were seen in about 1/3 of our sample, but they were more sluggish than those recorded in the superior gyrus. A prominent feature was suppression of on-going activity, which we found in about 1/3 of middle and in some superior temporal gyrus neurons. This suppression could precede vocalization by up to a few hundred ms, and could outlast it by up to 1 s. Evoked ECoG-potentials to words heard or spoken were different, and those to overt speech were more widespread.

Emotions↗
PubMed1989

Neuronal activity in the human lateral temporal lobe. III. Activity changes during music.

During open brain surgery under local anesthesia for the treatment of medically intractable temporal lobe epilepsy we have recorded neuronal activity from the lateral temporal lobe with microelectrodes while the patients listened to short pieces of music. Three groups of music were tested: A) Simple familiar or unknown classical tunes at a simple rhythm and harmony, played on piano; B) Orchestrated folk music; C) Drumming without a tune. All types of music lead to changes of neuronal discharge rate. Musical pieces of type A produced a decrease in 48% of the recordings, an increase in about 17% and had no effect in 30%. A similar distribution of effects was found during type B-music (48%, 22%, 30%, respectively). During type C, only 26% showed a decrease and 74% an increase. When music was turned off, usually the reverse change from that caused by music was seen. In addition to changes of discharge rate, a slight entrainment of activity by single, regularly appearing notes (rhythm) was seen in some neurons. A few neurons showed a change of activity related to musical phrases (activation towards the end of a 4-bar 4/4 phrase). In contrast to the effects of verbal stimuli and overt speech, the effects of music on discharge rates did not show obvious topographical differences between superior, middle and inferior temporal gyrus. They also were bilateral with no significant right-left differences.

Acoustic Stimulation↗
PubMed1988

Neuronal activity in human lateral temporal cortex related to short-term verbal memory, naming and reading.

Extracellular microelectrode recordings were obtained from lateral temporal cortex that was subsequently resected in patients undergoing craniotomies under local anaesthesia for treatment of medically intractable epilepsy. During these recordings patients performed visually presented measures of overt and silent naming and word reading, short-term verbal memory and a control task requiring matching of angles. These measures were designed so that the same visual stimuli elicited language, short-term memory or spatial responses. Statistically significant changes within and between these various measures were identified. Technically satisfactory recordings were obtained from 17 populations reflecting activity predominantly from 1 neuron, in 13 patients. Two populations demonstrated no significant changes in any measured functions. Only 1 population showed changes suggesting a relation to visual perception. Four populations in or adjacent to the superior temporal gyrus altered activity with overt speech. Four other populations in the anterior temporal lobe altered activity during silent, but not overt speech. Some relation to language or memory was established for 13 of the 17 populations: 1 altered activity during reading alone, 6 during memory alone, and 6 to both. Most of the recording sites showing these language and memory changes were not essential for those functions based on surface electrical stimulation mapping. Thus the area of temporal lobe that participates in language and memory, as indicated by changes in neuronal activity, is substantially larger than the areas essential for those functions as determined by stimulation mapping. Within that participatory area, changes related to language were most often an increase in activity sustained throughout the task, a pattern suggestive of mechanisms of selective attention. Changes related to memory most often included a sustained increase in activity at the time of entry of information into memory, and again at retrieval, with decreased activity during the time the memory was stored. A few neuronal populations demonstrated relative inhibition of activity during the memory task, compared with control measures.

Electric Stimulation↗
PubMed1987

Darkness induction, retinex and cooperative mechanisms in vision.

We have investigated the darkness induction of surround fields of various composition on a centrally located test field. Darkness induction can be described as a linear subtraction of the luminance of the induction region from the test field luminance, weighted for the size, the length of immediate contact and the distance of the induction field from the test field. Furthermore, closer induction fields exert a shunting effect on the induction effect of fields which are more distally located on the same radius, and neighbouring fields mutually interact. A model is discussed which takes into account these variables. It is compared with older models as well as with the Retinex-model as formulated by Land (1983). Our data and model are closer to the model of Jameson and Hurvich (1964). Neurophysiological correlates and mechanisms are discussed.

Adult↗
PubMed1986

Colour and brightness signals of parvocellular lateral geniculate neurons.

We recorded from single neurons in the parvocellular layers of the lateral geniculate body of anesthetized monkeys. Spectral response curves of parvocellular neurons depended on the luminance ratio between the chromatic stimuli and achromatic background. From response/intensity curves, we determined the relative luminance between a coloured and an achromatic (white) light at which a given cell became non-responsive (critical luminance ratio, CLR). The spectral dependence of the CLRs of narrow (N) and wide band (W) cells with opponent receptor input showed characteristic differences. The activity of W-cells increased with luminance increase of a white light and of a coloured light in the specific spectral region of the cell (yellow-red for the long wave length sensitive WL-, and yellow-green-blue for the short wave length sensitive WS-cells), while N-cells were activated by their specific spectral light (blue for NS-cells, red for NL-cells) and by a luminance decrease of achromatic white. N-cells discriminate best between their characteristic colour and white at luminance ratios below their respective CLR, while W-cells distinguish best between a light of their characteristic colour and white at chromatic/achromatic luminance ratios above their respective CLR. Yellow sensitive W-cells with a narrow spectral sensitivity peaking around 570 nm and with only a small or no response to white light, could enable distinction between white and yellow of similar luminance. The findings are consistent with the opponency model of spectrally sensitive cells in the LGB. We discuss their implications for colour coding by parvocellular cells. N- and W-cells appear to behave complementary with respect to luminance information (N-cells may be compared to the cat's off-cells, W-cells to on-cells). S- and L-cells are complementary with respect to colour. The yellow sensitive WM-cells are critical for the discrimination of yellow and white, while cells with excitatory cone input from blue and red cones (W-SL-cells) may aid the perception of purple. The fact that, at different relative luminance ratios between a chromatic stimulus and a white background, the whole family of parvocellular cells is involved differently in coding for colour, may explain the different appearance of colours against a white background at different luminance ratios and the perception of induced colours.

Animals↗
PubMed1984

The second, intralaminar thalamo-cortical projection system.

In the marmoset (Callithrix jacchus), HRP and 3H-apo-HRP were injected into various cortical regions and the positions of labelled neurons in the non-specific, intralaminar thalamic nuclei (N. centralis and centre m edian ) were investigated. Although neuron populations projecting to the different cortical regions overlap widely, a coarse topology exists inasmuch as intralaminar neurons projecting to the posterior cortex were located more rostrally and those projecting to the anterior cortex were located more caudally in the intralaminar complex. With injections into nearby cortical regions of the parieto-temporal association cortex with HRP and 3H-apo-HRP, respectively, no double labelled cells were found in the intralaminar nuclei, although the fields of labelled cells completely overlapped. Also in the specific projection nuclei no double labelled cells were encountered. About 10-20% of the thalamo-cortical projection cells are located in the intralaminar nuclei. Some functional aspects of this second thalamo-cortical projection system are discussed.

Animals↗
PubMed1984

The representation of contrast and other stimulus parameters by single neurons in area 17 of the cat.

The responses of neurons in area 17 were tested as a function of various stimulus parameters. The thresholds of individual cortical neurons were at contrasts between 0.01 and 0.1 (increment of 0.5 X 10(-1) cd/m-2 on a background of 3 cd/m-2), the dynamic ranges were 1.0-2.0 log units of increment, and all cells showed a response decrease at increments above a certain maximum (supersaturation response). The averaged contrast/response curve for all neurons was S-shaped in the logarithmic plot, had a dynamic range of 2.5 log units, reached its maximum at a contrast of 0.75 and supersaturated above this level. The contrast/sensitivity curves changed their slope under different stimulus conditions. They became flatter when the non-dominant eye was stimulated as compared to dominant eye stimulation or when the stimulation was done at a non-optimal orientation or direction, and they became steeper when both eyes were stimulated. But the maximum was reached at the same contrast and supersaturation was seen above maximum contrast no matter whether a cell was strongly (e.g. binocular stimulation at optimal orientation) or weakly excited (non-dominant or non-optimal orientation stimulation). After normalization, the averaged population contrast/response curves were virtually identical at all stimulus conditions. It was concluded, that range as well as maximum and supersaturation of cortical contrast/response curves are determined before the input reaches the cortex, and that the cortical cells summate, essentially, linearly. The findings furthermore demonstrate that the supersaturation of the cortical input must be due to subtractive inhibition, and that the same is true for the orientation sensitive inhibition in the cortex itself. Both, the peripheral contrast and the cortical orientation dependent inhibition cannot be explained by multiplicative inhibition. The fact, that the responses of neurons depend on many variables relativates their significance for feature representation.

Animals↗
PubMed1982

Physiologic and anatomic investigation of a visual cortical area situated in the ventral bank of the anterior ectosylvian sulcus of the cat.

In this paper a cortical area is described that covers approximately the posterior two-thirds of the ventral bank of the anterior ectosylvian sulcus of the cat and is called anterior ectosylvian visual area (AEV). In cats anesthetized with a combination of N2O and barbiturate we explored this area by recording extracellularly the responses of AEV neurons to visual and electric stimulation as well as by injecting HRP into physiologically verified points. AEV neurons were found to be highly sensitive to small light stimuli moving rapidly in a particular direction through their large receptive fields. The properties of 74 neurons were quantitatively analyzed. Increasing the length of the stimulus within the receptive field to more than 2 deg strongly inhibited the responses, whereas increasing the speed of the stimulus movement up to 72-120 deg/s enhanced the neuronal responsiveness. Although the majority of neurons responded to a wide range of possible directions, one clearly preferred direction could usually be found for each neuron. There was predominance of preferred directions toward the contralateral hemifield. Anatomic and electrophysiologic connectivity studies showed that AEV receives its main afferent inputs from the lateral suprasylvian visual area (LS) and from the tecto-pulvinar complex. Although these studies suggested some topographical organization within the projection from LS to AEV, the large receptive fields in AEV, the great majority of which included the central area, did not reveal a clear retinotopic order. It is concluded that AEV is a specific visual area and that functionally the extrageniculate inputs predominate.

Animals↗
PubMed1980

Thalamocortical transformation of responses to complex auditory stimuli.

In unanesthetized guinea pigs, thalamic (CGM), and cortical (auditory I) neurons were recorded simultaneously. Nine of 69 neuron pairs showed a positive cross-correlation of their spontaneous activities, with increased discharge probability of the cortical neuron beginning 2--5 ms after the discharge of the CGM-neuron. The individual neurons of such pairs had an identical CF and the same spectral responsiveness. The responses of cortical neurons to pure tones were much more phasic than those of the corresponding CGM-neurons. Thalamic neurons could be driven up to much higher AM- and FM-modulation frequencies (100 Hz) than cortical neurons, which usually ceased to follow AM-frequencies above 20 Hz. Stronger or weaker suppression of tonic response components in cortical and thalamic neurons and the lower AM-range of cortical neurons is related to stronger or weaker intracortical and intrathalamic inhibition respectively. Response characteristics to FM-stimuli are similar to those of AM-stimuli. All CGM and cortical neurons responded to a variety of natural calls of the same or of other species. Responses of CGM-cells represented more components of a call than cortical cells even if the two cells were synaptically connected. In cortical cells, repetitive elements of a call were not represented if the repetition rate was too high. High modulation frequencies within a call, such as those of the fundamental frequency, could still be separated in the response of some CGM-neurons, but never in those of cortical neurons. Both CGM and cortical cells responded essentially to transients (amplitude or frequency modulations) within a call, if spectral components of such elements were within the spectral sensitivity of the cell. Spectral components outside the spectral sensitivity range could result in suppression of spontaneous discharge rate. Responses of cortical and CGM-cells, and thus the representation of call elements by neuronal responses, varied with the intensity of a call. It is suggested that, at higher levels of the auditory system, essential information about the temporal features of complex sounds may be represented by neural responses to transients in various spectral regions.

Animals↗