Personal examples of observations in cognitive science are sketched, and open questions, theoretical consequences and some applications derived from this research are indicated. The importance of interdisciplinarity in cognitive science is stressed. Neuropsychological and psychophysical observations on visual perception are described, and the usefulness of single case studies is emphasized. Psychophysical and neurophysiological observations indicate discrete temporal processing as reflected in “time windows” in the sub- and supra-second domain. For neural and behavioural oscillations (or oscillations in general) a statistical tool is suggested. In a taxonomy of functions the distinction between content functions and logistic functions in cognition and their complementarity in subjective representation is outlined. For
these personal research domains references are given at the end. These differently looking domains share a common conceptual frame with respect to content, methodology and theoretical considerations.
To evaluate one’s own research retrospectively is a challenging task as one has to take an external perspective to oneself. Several questions arise in such an endeavour: Did one actually discover something that deserves the term “discovery”? Did one make observations not known before? Did one formulate relevant or interesting new questions? Did one participate in the formulation of new concepts? Did past contributions open trajectories for new research? Did the research lead to practical applications? How does one do research anyway? One should be modest, but one should also not shy away to indicate what has been achieved with satisfaction, perhaps sometimes even with pride. A criterium in this reflective retrospection is that it is actually not so important whether it is noticed or even acknowledged by others what has been done. The criterium is anchored only in oneself. Acknowledgment by others is a positive side-effect (although sometimes for wrong reasons). This personal criterium does not imply that one should not communicate what has been done. Research happens in a social environment and communication is also demanded by society whose financial support makes research possible.
What follows in this description are several examples that reflect an interdisciplinary approach as I understand it in doing research in cognitive science. It is necessary, however, to distinguish two modes of interdisciplinarity, the vertical and the horizontal approach. In vertical interdisciplinarity one tries to link bidirectionally different levels of data generating processes on the cellular (even molecular), the inter-cellular, and the modular level with whole brain activities and furthermore with the behavioural and experiential subjective level up to even aesthetic appreciations. In horizontal interdisciplinarity different domains of research are connected bidirectionally; examples are psychology and physics (“psychophysics”), neuroscience and aesthetics (“neuroaesthetics”), neuroscience and philosophy (“neurophilosophy”), or basic research with technological applications or methodological developments. Although conceptually one can differentiate between the two domains, in reality “complementarity as a generative principle” applies (Zhao et al. 2022): to
make progress in vertical interdisciplinarity new technologies in horizontal interdisciplinarity may have to be developed, or observations in horizontal interdisciplinarity may trigger in vertical interdisciplinarity new horizons.
In visual perception a discovery is residual vision or “blindsight” as it is mostly referred to now (Pöppel, Held and Frost, 1973). This phenomenon would be an example for vertical interdisciplinarity. It has for instance been observed that in non-human species after an ablation of the visual cortex the animal still can orient in visual space. Human patients with equivalent injuries in the visual cortex suffer absolute blindness in retinotopically corresponding areas in the visual field. The question came up why there is a discrepancy between non-human primates and human patients in spite of the high similarity of anatomical structures in the visual pathway. Maybe “asking “patients to give an answer whether they see something or not is not a good way to check whether visual information is still processed. Possibly some behaviour may not have access to a verbal or conscious representation. When such patients are required to automatically direct their gaze to a visual stimulus they do not “see” or when they have to guess which feature a visual target might have, it could be shown that on an implicit level visual information without conscious representation is still processed. In spite of initial severe criticism “blindsight” as a phenomenon is now well established. It has given rise to horizontal interdisciplinarity as it has initiated discussions in philosophy about what “consciousness” could mean. It has opened new horizons for rehabilitation of function. Furthermore, blindsight stresses the importance of implicit (or tacit) knowledge complementary to explicit knowledge.
Sometimes a perceptual phenomenon may come as a surprise as it happened in blindsight research. With a well-known blindsight patient who had been studied by several international research groups, I could observe conscious vision across an extended area of blindness for moving but not for stationary stimuli. (It should be noted that this discovery was a consequence of serendipity which proves the importance of observational openness for the unexpected). This visual completion effect for horizontally moving vertical stimuli is shown to be of perceptual and not of conceptual origin, most likely mediated by spared representations of the visual field in the striate cortex. The neural output to extra-striate areas has been shown to be still intact; this is for instance indicated by preserved size constancy of visually completed stimuli. Neural responses as measured with fMRI reveal an activation only for moving stimuli, but strangely enough on the ipsilateral side of the brain. In a neuro-conceptual model this shift of activation to the “wrong” hemisphere can be explained on the basis of an initiated disbalance of excitatory and inhibitory interactions within and between the striate cortices in the left and right side of the brain. The observed neuroplasticity and the behavioural observations provide important new insights into the functional architecture of the human visual system (Pöppel, 1985; Bao et al. 2023, under review). This example of vertical interdisciplinarity also proves the usefulness of a “psycho-anatomical” paradigm.
Single case studies as in blindsight research, in neuropsychology or in cognitive science in general have indeed been proven to be of practical relevance. In another single case study it could be shown that colour induction is a retinal phenomenon not being the result of cortical processing (Pöppel, 1986; Zhou et al, 2016). What is colour induction? If an after-image is created one observes that lateral to the after-image the same original colour is induced that created the negative or complementary after-image in the first place. If this area in the visual field has no cortical representation because of a central injury colour induction is still observed. Thus, this phenomenon cannot be of cortical origin; it must be retinal. Furthermore, this observation implies the existence of a lateral inhibitory network at the retinal level selective for different spectral components; because of the retinal anatomy this network is presumably implemented at the level of amacrine cells. This observation is an example of vertical interdisciplinarity as it makes a prediction from the observational level to the level of a local neural implementation.
Sometimes it happens to be a single case oneself. In studying the distribution of sensitivity throughout the visual field I observed that the subjective brightness of threshold stimuli is increasing towards the periphery of the visual field in parallel to the decrease of sensitivity. Apparent brightness is apparently directly related to the physical intensity of visual stimuli. This should not come as a surprise, but the question has to be answered why the brightness of stimuli at threshold for different locations in the visual field is not always the same as one would predict on the basis of psychophysical laws. It has to be assumed that the summation properties of retinal ganglion cells do not have the typical sigmoid characteristics for all retinal positions, but that for more peripheral positions in the visual field an inhibition of summation is implemented at threshold resulting in the subjective phenomenon of increase of brightness for more peripheral targets; this contradicts in particular Fechner’s law in psychophysics, but it explains constancy of brightness throughout the visual field under photopic adaptation (Pöppel and Harvey, 1973; Zhou et al., 2016; Zihl et al., 1980).
The measurements on sensitivity resulted in addition to an unexpected discovery: the human visual field is characterized by a plateau of constant sensitivity between some 10 to 35 degrees eccentricity along the horizontal meridian. This plateau is surrounding the perifoveal region up to some 10 degrees eccentricity which shows a decreasing sensitivity from the fovea until this border under photopic adaptation. This specific distribution pattern of the perifoveal and peripheral regions of sensitivity matches the distribution of ganglion cells in the human retina. Does this inhomogeneity reflect functional differences? This is indeed the case. An “eccentricity effect” was discovered with the paradigm of inhibition of return that indicates different attention mechanisms for perifoveal and peripheral regions of the visual field (Bao and Pöppel, 2007; also Pöppel et al., 1975). Such a dissociation of attention matches retinal projections to the colliculus superior for the more peripheral areas and to the lateral geniculate nucleus for the fovea and perifoveal areas.
Mapping of Spaces
Sometimes the combination of two problems can be the basis of a new insight. A patient with a convergent squint in one eye since birth suffered a unilateral occipital lobe injury as an adult. These two problems allowed to study the relationship between visual field representation and oculomotor map. Targets at different locations in the visual field trigger saccadic eye movements matching the eccentricity of the targets. What would happen if the two visual axes are no longer aligned when one eye suffers a squint? In this single case study rigidity of visual field representation could be shown: the vertical meridian of the squinting eye was shifted in the perimetric analyses by the angle of the squint. However, plasticity for oculomotor control for the squinting eye was shown as lateral eye movements are programmed with respect to a functional pseudo-fovea and not the projection of the anatomical fovea (Pöppel et al., 1987). Mapping of spaces and their potential dissociation poses also a problem for different sensory modalities. The visual field is mapped onto the visual cortex with respect to retinal coordinates; as auditory mapping is related to head coordinate it follows that the mapping of auditory receptive fields indicating locations in auditory space cannot correspond directly to the map of the visual field in organisms with lateral eye movements as such movements result in a mismatch of the two projection systems. Thus, a map adaptation between these modalities has to take place to align the two coordinate systems (Pöppel, 1973). (This phenomenon has been referred to by some colleagues as “Pöppel’s Paradox”.)
Restitution of Visual Function
Rare single cases with unique perceptual problems can provide the basis for further experimental considerations. A patient suffering from tunnel vision after a bilateral occipital lobe infarction showed substantial restitution of function in the expansion of the functional visual field after visual training; he was presumably the first patient in which this kind of restitution has been demonstrated. Interestingly, the improvement of function showed an interesting temporal feature: During each training session lasting for approximately one hour the functional competence got worse, but in the long run improvement was observed. It can be speculated that possibly short-term “central fatigue” or reduction of synaptic efficacy was a necessary pre-requisite for long-term improvement (Pöppel et al, 1978; Zhou et al., 2016). This raises the general question for perceptual learning or learning in general about the interaction of short-term and long-term performance.
The patient with tunnel vision showed also a unique phenomenon in binocular rivalry when vertical stripes of one color and horizontal stripes of another color were shown. Whereas in typical situations the switching rate or period in binocular rivalry has a modal value of a few seconds, this patient showed an extreme slowing down with tens of seconds for either percept. More interesting than the slowing down itself was the description of the perceptual change: vertical stripes of one color were gradually “pushing away” the horizontal stripes of the other color; then after one percept was completed the reverse “pushing away” of the other color was initiated; and this extreme slowing down of perceptual reversal continued in a wave-like fashion. Thus, it can be argued that the brain injury provided something like a “temporal microscope” in neural processing. This leads to the general question how in the time domain percepts are constructed. Are percepts implemented either at all positions on the representational surface simultaneously, or alternatively with a high frequency wave being initiated at distinct locations?
Discrete Temporal Processing
It has become like a dogma in cognitive science that reaction time distributions or response distributions in general are unimodal and even showing a Gaussian pattern. The implicit hypothesis of this unquestioned assumption is that temporal processing in neural systems is of continuous nature, in fact reflecting the theoretical concept of continuous time in classical physics. On the basis of this assumption numerical differences of reaction times under defined cognitive conditions are used to extract sequential processing stages. However, are such statistical distributions in fact unimodal? Under controlled experimental conditions in measurements of reaction time guaranteeing stationarity there is strong evidence that reaction time distributions are multimodal, and this statistical feature is observed for different sensory modalities (Bao et al., 2016; Pöppel, 1970). Such multimodality is also seen in latency distributions of saccadic and pursuit eye movements. Importantly, in these cases the intermodal distance is 30 to 40 milliseconds reflecting central excitability cycles. Thus, temporal processing in neural systems is not continuous but discrete. Sensory stimuli entrain instantaneously an oscillatory process which is typical for relaxation oscillations; motor responses are triggered at the same phase in successive periods. In contrast, in a pendulum oscillation without an instantaneous phase shift stimuli would occur at any phase of the oscillation and therefore multimodality could not be explained. Thus, multimodal response
distributions of reaction times answer two questions: temporal processing in neural systems is discontinuous or discrete and relaxation oscillations can be assumed as the underlying neural mechanism. It can furthermore be hypothesized that each period of such an oscillation represents a time window in which information is integrated (Pöppel et al., 1990). Indeed, there is substantial additional evidence for a time window with a duration of some tens of milliseconds as in temporal order threshold for visual, auditory and tactile stimuli, in temporal tolerance of stereopsis, in sequential scanning in working memory, in anticipatory control of movements, or in single cell activities for instance in the ascending visual pathway (Bao et al., 2015). Thus, employing the Baconian or Darwinian concept of induction by collecting and unifying observations from different experimental and observational domains there is strong evidence for a time window of some tens of milliseconds as a neural processing unit. Loss of Consciousness in Anaesthesia An indicator of this time window is also the mid-latency response of auditory evoked potentials. Using power spectral analysis or other statistical tools in time series analysis (Li et al., 2018) the successive components of the mid-latency response can be treated as a neural
oscillation with a frequency of some 40Hz. It has been discovered that this oscillatory component disappears under anesthesia with general acting anesthetics (like propofol or isoflurane), although brainstem potentials can still be observed (Madler and Pöppel, 1987; Schwender et al., 1994). On the subjective level temporal processing is completely suppressed; there is no event detection at all. A typical question of a patient after the anesthetic state is “when does the operation begin”. Thus, this state of an absolute loss of consciousness is radically different from normal sleep. The suppression of the mid-latency response of the auditory evoked potential and the loss of consciousness suggest that the short-term time window indeed represents processing units of neural activity, and that their functionality is a necessary condition for conscious representations. It has to be emphasized that for those anesthetics which do not suppress the oscillatory component of the auditory evoked potentials this loss of temporal processing is not observed. Hypothetically, a disruption or in particular a desynchronization of local elements in the thalamo-cortical network is responsible for the loss of consciousness. This research is an example of a practical application of basic research and represents both vertical and horizontal interdisciplinarity.
It is a question since ages, in particular in philosophy, what the “present” could be. Is it just a point in time or does it have a duration that can be measured? From a pragmatic point of view one can define the present as the subjective state of consciousness implemented in a time window of some three seconds. What is the empirical evidence that supports such a pragmatic definition? Empirical evidence comes from behavioral studies and neurophysiological observations, and one is invited again to employ the Baconian or Darwinian approach to extract a general phenomenon. Here are a few examples: In
experiments on the reproduction of temporal intervals in the visual and auditory modality one observes an overestimation of short and an underestimation of long intervals with an indifference point at some three seconds (Pöppel, 1997). The temporal machinery of this time window is uncovered in a particular patient group who reproduce all intervals with some
three seconds reflecting the eigenvalue of an underlying neural process (Szelag et al., 2004). The three second time window has been found in spontaneous behavior and movement patterns for members of different cultures (Schleidt et al., 1987). The reversal rate of visual and auditory ambiguous stimuli shows the same time window. The segmentation of spontaneous speech in different languages has the same value. In studies on inhibition of return attention control is limited to this time window (Bao et al., 2013). In sensorimotor synchronization one can anticipate precisely stimuli up to three seconds but not beyond (Mates et al., 1994). Cortical sensitivity fluctuates with a period of some three seconds as
measured with mismatch negativity (Wang et al., 2015). These and many other examples with different experimental paradigms prove the existence of this time window which, however, should not be understood as a physical time constant but as an operating range to be modeled best with relaxation oscillations. But what is it good for? One suggestion is - taking an evolutionary perspective - that the time window of some three seconds as a logistic function of neural processing serves the purpose of creating and maintaining the identity of something as something, like a specific percept or mental content in general for some time, but not forever. Thus, the time window may reflect “complementarity as a generative principle” in providing time-limited stationarity and temporal dynamics referring to successive time windows (Zhao et al. 2022).
Interestingly, the time window of three seconds is also observed in cultural artefacts. As indicated above spontaneous speech in different language environments shows a temporal segmentation with some three seconds. This segmentation seems to be carried over to poetry. It was found that the verse length of poems is temporally embedded in this time window (Turner and Pöppel, 1983). If the poet follows this apparently implicit rule of temporal organization the poem shows a particular aesthetic quality. If artificially the natural verse length is lengthened or shortened the poems loose in aesthetic appreciation. Although the hexameter is characterized by a longer verse length, the caesura within a line creates again a temporal segmentation. In music one also finds the dominance of this time window: In classical music the duration of motifs matches the subjective present of approximately three seconds. In addition to poetry and music one observes in films a shot duration with a preference of some three seconds validating this temporal rule. As cultural artefacts exhibit the time window of some three seconds, these observations can be considered as a indeed unique support for the neural implementation of a pre-semantically defined time window (Pöppel, 2009). Even within very different cultural trajectories the temporal organization principle is maintained as an anthropological universal (Bao and Pöppel, 2012). The freedom of artistic expression is limited, and if the limits are transcended endogenous aesthetic appreciations are modified. Thus, an evolutionary basis of the aesthetic sense is implied.
De-Synchronization of Circadian Rhythms
Within an evolutionary frame two kinds of time windows in temporal processing have to be distinguished, i.e., those that represent behavioral adaptations to geophysical cycles in nature like the circadian or annual cycle, and those that reflect self-organization in neural processing like the time windows of tens of milliseconds and of some three seconds. (As a side-remark it should be emphasized that the importance of the circadian rhythm is often overlooked in cognitive science when for instance the time of day is not controlled in behavioral experiments. The problem of non-repeatability of results in psychology may be also due to the fact that the circadian phase in measurements was neglected.) The endogenous nature of circadian rhythms dominating behavior has been established in experiments when subjects were completely isolated for a longer time from the external environment. Under normal circumstances humans and many other organisms are synchronized by the light-dark-cycle, the nucleus supra-chiasmaticus in the hypothalamus being a crucial structure to guarantee in humans the embedding of behavior in the physical environment. The question came up whether social synchronization is also possible when excluding the light-dark-cycle. This is indeed the case (Bao et al., 2015; Pöppel, 1968) with an additional unexpected result. Proving again the importance of single cases in this research domain it was observed in one subject that social synchronization took place in parallel to internal desynchronization; being socially with others destroyed the internal time structure of this subject. This desynchronization showed a very specific feature; it resulted physically speaking in a beat phenomenon for vegetative functions like body temperature and kidney functions. For a certain interval the circadian rhythms were in phase and showed a typical diurnal variation, then this variation was no longer detectable, and after some tine returning again. Thus, two circadian rhythms were super-imposed with a slightly different period. This unique observation has apparently not been described again, and it belongs in this personal retrospection to the unnoticed discoveries.
Non-Parametric Time-Series Analysis
To detect circadian or other biological rhythms, or rhythms in general, statistical tools are necessary, in particular if they are shadowed by noise. A practical problem is that measured time series because of external circumstances are sometimes not long enough to obtain a data set that is sufficient to identify the precise frequency of the suspected oscillation. It may even happen that only one or two periods are observable as in the case of mid-latency auditory potentials. Is there a way out to overcome this problem? An interactive non-parametric method can take care of this challenge (Li et al., 2018; Miescke and Pöppel, 1982; Pöppel, 1970). For a time series with length n, an analysis interval with length k is chosen, which is approximately half of the suspected period; the selection of a suspected half-period is the essential feature of this interactive method. A rank correlation coefficient is computed between the natural number sequence 1, 2, ... k, and the first to the kth value within the chosen analysis interval of the half-period after the measured values have been transformed into their rank numbers. In the next steps, the correlation coefficients are computed again between the natural number sequence 1, 2, ... k and the second to the k+1th value (using again their transformed rank numbers within the analysis interval), then the third to the k+2th value and so on, until the end of the time series is reached. In this way, one obtains a series of rank correlation coefficients for the entire time series. This set of correlation coefficients is followed by statistical inference to extract the period using standard tools like the chi-square-test to compute the probability whether the sequence of correlation coefficient is randomly distributed or not. The method is phase insensitive; thus, observations with only a few periods can be glued together to form a longer sequence to be analyzed.
Taxonomy of Functions
It may come as a surprise if it is claimed that there is no taxonomy of functions that the research community in cognitive science agrees upon (Pöppel and Ruhnau, 2011). This is different from chemistry or biology which are characterized by generally accepted taxonomies. Of course, there are so-called “textbook taxonomies” with the different chapters of cognitive functions, and other organizational frames as implicit taxonomies. A typical implicit taxonomy would be psychophysics in which cognitive functions are mapped onto physical parameters of the objective world which actually implies that the taxonomy is physical. One disadvantage is that many subjective phenomena are not included. Another implicit taxonomy has its basis in language: Here it is assumed that subjective phenomena map isomorphically onto language, but this organizational frame neglects implicit or tacit knowledge (Bao et al, 2022; Pöppel and Bao, 2012). Is there a way out of this taxonomic dilemma? It is believed that a taxonomy can find a basis in neuropsychological or psychiatric observations and in evolutionary principles (Pöppel, 1989); this conceptual approach also takes care of anthropological universals and cultural specifics (Bao and Pöppel, 2012). What is the main argument? In this taxonomy the existence of any function in the cognitive machinery is proven by its loss or its disruption. Two functional domains have to be distinguished (Zhao et al., 2022): content functions that represent the repertoire of subjective experiences (like percepts, memories, emotions, or volitions) and logistic functions that guarantee the availability of content (like the temporal organization with time windows, the different attention systems, and general activation). This complementarity is reminiscent of a famous statement of Immanuel Kant in the “Critique of Pure Reason”: “Gedanken ohne Inhalt sind leer, Anschauungen ohne Begriffe sind blind” (Thoughts without content are empty, intuitions without concepts are blind). This would be an example of horizontal interdisciplinarity.
Yan Bao, Ernst Pöppel: Two spatially separated attention systems in the visual field:
evidence from inhibition of return. “Cognitive Processing” 8 (2007) 37-44
Yan Bao, Bin Zhou, Xinchi Yu, Lihua Mao, Evgeny Gutyrchik, Marco Paolini, Nikos
Logothetis, Ernst Pöppel: Conscious vision in blindness: a new perceptual phenomenon
implemented on the “wrong” side of the brain. “PsyCh Journal”, 2023, under review
Ernst Pöppel: Comment on "Visual system's view of acoustic space". “Nature” 243 (1973)
Ernst Pöppel: Bridging a neuronal gap: Perceptual completion across a cortical scotoma is
dependent on stimulus motion. “Naturwissenschaften” 72 (1985) 599
Ernst Pöppel: Long-range colour-generating interactions across the retina. “Nature” 320
Ernst Pöppel, Rüdiger Brinkmann, Detlev von Cramon, Wolf Singer: Association and
dissociation of visual functions in a case of bilateral occipital lobe infarction. “Archiv für
Psychiatrie und Nervenkrankheiten“ 225 (1978) 1-22
Ernst Pöppel, Lewis O. Harvey, Jr.: Light-difference threshold and subjective brightness in
the periphery of the visual field. “Psychologische Forschung” 36 (1973) 145-161
Ernst Pöppel, Richard Held, Douglas Frost: Residual visual function after brain wounds
involving the central visual pathways in man. “Nature” 243 (1973) 295-296
Ernst Pöppel, Detlev von Cramon, Helmut Backmund: Eccentricity - specific dissociation of
visual functions in patients with lesions of the central visual pathways. “Nature” 256 (1975)
Ernst Pöppel, Petra Stoerig, Nikos Logothetis, Wolfgang Fries, Klaus-Peter Boergen,
Wolfgang Örtel, Josef Zihl: Plasticity and rigidity in the representation of the human visual
field. “Experimental Brain Research” 68 (1987) 445-448
Bin Zhou, Ernst Pöppel, Lingyan Wang, Taoxi Yang, Yuliya Zaytseva, Yan Bao (2016).
Seeing without knowing: Operational principles along the early visual pathway. “PsyCh
Journal”, 5: 145-160. DOI: 10.1002/pchj.141
Josef Zihl, Peter Lissy, Ernst Pöppel: Brightness perception in the visual field: Effects of
retinal position and adaptation level. “Psychological Research“ 41 (1980) 297-304
Yan Bao, Ernst Pöppel, Lingyan Wang, Xiaoxiong Lin, Taoxi Yang, Mihai Avram,
Janusch Blautzik, Marco Paolini, Sarita Silveira, Aline Vedder, Yuliya Zaytseva,
Bin Zhou (2015): Synchronization as a biological, psychological and social mechanism to
create common time: A theoretical frame and a single case study. “PsyCh Journal” 4:
243–254. DOI: 10.1002/pchj.119
Yan Bao, Zhiyuan Wang, Wei Liang, Yi Wang, Ernst Pöppel, Hui Li: Inhibition of return at
different eccentricities in the visual field share the same temporal window. “Neuroscience
Letters” 534 (2013) 7-11
Yan Bao, Taoxi Yang, Xaoxiong Lin, Ernst Pöppel (2016). Donders revisited: Discrete or
continuous temporal processing underlying reaction time distributions? “PsyCh Journal” 5:
177-179. DOI: 10.1002/pchj.142
Christian Madler, Ernst Pöppel: Auditory evoked potentials indicate the loss of neuronal
oscillations during general anaesthesia. „Naturwissenschaften“ 74 (1987) 42-43
Jiri Mates,Ulrike Müller, Tomas Radil, Ernst Pöppel: Temporal integration in sensorimotor
synchronization. „Journal of Cognitive Neuroscience“ 6 (1994) 332-340
Ernst Pöppel: Desynchronisationen circadianer Rhythmen innerhalb einer isolierten Gruppe
(Desynchronization of circadian rhythms in an isolated group). „Pflügers Archiv“ 299 (1968)
Ernst Pöppel: Excitability cycles in central intermittency. “Psychologische Forschung“ 34
Ernst Pöppel: A hierarchical model of temporal perception. “Trends in Cognitive Sciences” 1
Pöppel, Ernst (2009). Pre-semantically defined time windows for cognitive processing.
Philosophical Transactions of the Royal Society B. 364, (2009) 1887–1896
Ernst Pöppel, Kerstin Schill, Nicole von Steinbüchel: Sensory integration within temporally
neutral system states: A hypothesis. “Naturwissenschaften” 77 (1990) 89-91
Margret Schleidt, Irenäus Eibl-Eibesfeldt, Ernst Pöppel: A universal constant in temporal
segmentation of human short-term behavior. “Naturwissenschaften” 74 (1987) 289-290
Dierk Schwender, Christian Madler, Sven Klasing, Klaus Peter, Ernst Pöppel: Anesthetic
control of 40-Hz brain activity and implicit memory. “Consciousness and Cognition” 3 (1994)
Elzbieta Szelag, Joanna Kowalska, Tadeusz Galkowski, Ernst Pöppel: Temporal processing
deficits in high-functioning children with autism. “British Journal of Psychology” 95 (2004)
Fred Turner, Ernst Pöppel: The neural lyre: Poetic meter, the brain and time. “Poetry“,
August (1983) 277-309
Lingyan Wang, Xiaoxiong Lin, Bin Zhou, Ernst Pöppel, Yan Bao (2015). Subjective present:
a window of temporal integration indexed by mismatch negativity. “Cognitive Processing”,
Statistics: Time Series Analysis
Xiang Li, Ernst Pöppel, Yan Bao (2018): A nonparametric method to detect oscillatory
components in short time series. “PsyCh Journal”, DOI: 10.1002/pchj.221
Klaus J. Miescke and Ernst Pöppel: A nonparametric procedure to detect periods in time
series. “Stochastic Processes and their Applications” 13 (1982) 319-325
Ernst Pöppel: Frequency measurement in time series data. „Life Sciences and Space
Research“ 8 (1970) 234
Yan Bao, Ernst Pöppel: Anthropological universals and cultural specifics: Conceptual and
methodological challenges in cultural neuroscience. “Neuroscience and Biobehavioral
Reviews”, 36 (2012) 2143-2146
Yan Bao, Dongxue Zhang, Chen Zhao, Ernst Pöppel, Vera Zabotkina. An Aesthetic Frame
for Three Modes of Knowing. “PsyCh Journal”, (2022) 1–9. DOI: 10.1002/pchj.588
Ernst Pöppel: Taxonomy of the subjective: An evolutionary perspective. In: J.W. Brown
(Ed.): “Neuropsychology of visual Perception”. Lawrence Erlbaum Associates, Hillsdale, N.
J., USA (1989) 219-232
Ernst Pöppel, Yan Bao: Three modes of knowledge as basis for intercultural cognition and
communication: A theoretical perspective In: Shihui Han, Ernst Pöppel (eds): “Culture and
Neural Frames of Cognition and Communication”, Springer-Verlag , Heidelberg, 2011, 215-
Ernst Pöppel, Eva Ruhnau: Psychologie als eine auf Modelle angewiesene Angelegenheit
ohne Taxonomie - eine Polemik. (Psychology as an enterprise without a taxonomy using
models – a polemic). “Nova Acta Leopoldina NF” 110, Nr. 377 (2011) 213-233
Chen Zhao, Paloma Enriquez, Morteza Izadifar, Ernst Pöppel, Yan Bao, Vera Zabotkina.
Complementarity of mental content and logistic algorithms in a taxonomy of cognitive
functions. “Psych Journal”, 1-7. (2022) DOI: 10.1002/pchj.602