The Manner Of Processing Sequential Stimuli In The Early Visual Areas Of Human

There exist two opposite viewpoint about how the successive stimuli is processed in the early visual areas.In the traditional model, people believed that successive stimuli is porcessed frame-by-frame in the early visual areas, it means that the early visual areas is a pipeline where the information is processed in very short time(several milliseconds) and then sended to the higher visual cortical areas. The stimuli would not leave behind any information trace in the early visual areas. This viewpoint has existed since psychology was borned.However, a recent animal study challeges the traditional model.The experimenter made multielectrode recordings from cat's primary visual cortex and applied methods from machine learning in order to analyze the temporal evolution of stimulus-related information in the spiking activity of large ensembles of around 100 neurons. Then they used sequences of up to three different visual stimuli (letters of the alphabet) presented and with intervals of 100 ms or larger.With this technology they proved that the network from which they recorded is endowed with distributed fading memory for stimulus properties and is capable of performing online computations utilizing information about temporally sequential stimuli. This result challenges models assuming frame-by-frame analyses of sequential inputs.Computer simulations of sparsely connected recurrent circuits of neuron-like processing units as well as theoretical analyses of related circuits with simpler (linear) processing units have shown that systems with fading memory exhibit powerful computational capabilities because they permit integration of stimulus information over time. However, now we do not know how the human's early visual areas process the sequential inputs.Another question is about Sensory memory. In case there was evidence for 'information trace'already in primary visual cortex, the data would allow for inferences on the mechanisms underlying perceptual phenomena such as visual persistence and iconic storage. Moreover, the lack of evidence for "information trace (memory)'would provide an important constraint for hypotheses on processing modes implemented in the early visual areas.To achieve the two goals mentioned above,We need investigate whether there would exist information of stimuli or not. we presented sequences of same or different stimuli and investigated whether information about preceding stimuli interferes the presentation of subsequent stimuli. The former case would provide strong evidence for the existence of fading memory, whereas the latter would be supportive of models favoring frame-by-frame analysis of successive stimuli.In the first experiment,we first use fMRI to find a kind of stimuli which only evokes activation in the early visual areas, and then use ERPs evoked by two same sequential stimuli to detect if there exists information trace in the early visual areas, we proved that the early visual areas would preserve information of the stimuli about 700-800ms. In other words, when process the sequential stimuli, the early visual areas calculate the time between them. In the second experiment, we use the same experimental paradigm and proved that when process the sequential stimuli, the early visual areas calculate the difference of position and orientation between them, Our results indicate that the early visual areas would process the sequential stimuli in a very complicated manner, and challenge the traditional models assuming frame-by-frame analyses of sequential inputs.In our experiments, we proved that the early visual areas of human can preserve information of the stimuli about 700-800ms. This time is almost equal to the Sensory memory. Moreover, because of Sensory memory's retinotopic organization and their noncategorical, feature-based responses.Considering that iconic memory declines with similar time constants as the retrievability of stimulus-specific information in the present experiment and is sensitive to masks, it is conceivable that we studied a related mechanism.