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Emergence of concentric double-opponent receptive field properties by applying independent component analysis to natural images
e382
Abstracts / Neuroscience Research 68S (2010) e335–e446
features defined by correlations (2) and by powers and correlations (3) outperformed those by powers (1). The results suggest that temporal patterns of ECoG signals carry information on visual objects for specific categories.
P3-h27 Functional properties of neurons in the cat posterior, medial lateral-suprasylvian area Kota S. Sasaki 1,2 , Izumi Ohzawa 1,2 1
doi:10.1016/j.neures.2010.07.1690
2
P3-h25 Correlated trial variabilities between single units in the cat visual cortex—Stimulus dependence and its relation with the firing rate tuning
Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan CREST, Japan Science and Technology Agency, Tokyo, Japan
We recorded multiple single units simultaneously from the primary visual cortex of an anesthetized cats. We developed high-density electrode arrays (eight-single electrodes array and four-tetrodes array) fitting to a single hypercolumn. We collected multiple single unit activities over 40 trials under moving bar stimuli of 16 different orientations. We calculated the correlation coefficient (Rsc ) of trial variabilities between simultaneously recorded unit pairs. 64% of unit pairs were found to have statistically significant correlations (N = 324/504, Bootstrap sampling test: P < 0.05). First, we examined whether Rsc reflected similarity of receptive fields of the unit pairs. We defined two signal correlations by the difference of optimal orientations (SCo ) and correlation coefficient between tuning curves (SCm ). Rsc did not show significant dependence on either SCo or SCm . Rsc also didn’t depend on the physical distance of the unit pairs. These independence suggested that Rsc was not likely to originate from common inputs. On the other hand, we confirmed that Rsc of some unit pairs showed significant orientation dependence (N = 49/314, 16%, Kruskal-Wallis test: P < 0.05). To identify the origin of the stimulus dependence, we at first computed correlation coefficient between Rsc and evoked firing rate. For unit pairs having similar optimal orientations (within 90◦ ), only 22% showed significant correlation. In addition, some unit pairs showed significant stimulus dependence of Rsc in spite of the fact that one unit had non-significant rate tuning. Those properties suggest that the origin of firing rate tuning does not necessarily explain stimulus dependence of Rsc .
Motion information is not readily available in retinal images, but must be computed from them along the visual pathway in the brain. Monkeys and cats have several brain areas that are important for motion information processing. To understand how visual information is transformed along the pathway, functional properties of neurons should be compared between different brain areas by using the same sets of stimuli and analyses. We carried out extracellular single unit recordings in PMLS, which receive strong inputs from areas 17/18, of paralyzed and anesthetized cats. The responses of each neuron were examined in the orientation and spatial frequency domain by using a subspace reverse correlation technique with sinusoidal gratings. In addition, to evaluate if the neuron was tuned to a constant speed across different spatial frequencies, its responses were probed by presenting drifting gratings of various spatial and temporal frequencies. These response properties were compared with those of area 17/18 neurons to examine how visual signals are encoded in individual cells in PMLS and transformed after the early stage of visual information processing in the brain. PMLS neurons showed delayed responses compared with area 17/18 neurons (later onset, time to peak and offset than area 17 cells; later onset and time to peak than area 18 cells). With regard to tuning to orientation and spatial frequency, PMLS neurons had similar parameters to area 17 neurons (orientation tuning bandwidth, preferred spatial frequency, spatial frequency tuning bandwidth). However, PMLS neurons had broader tuning bandwidth to orientation and preferred spatial frequency higher than area 18 neurons. A subset of PMLS neurons showed titled response profiles in the joint domain of spatial and temporal frequency, which is a distinct characteristic from area 17/18 neurons. These PMLS neurons were tuned to a constant speed across a range of spatial frequencies.
doi:10.1016/j.neures.2010.07.1691
doi:10.1016/j.neures.2010.07.1693
P3-h26 Relationship between orientation selectivity and spatiotemporal receptive field structure of the cat lateral geniculate neurons
P3-h28 Emergence of concentric double-opponent receptive field properties by applying independent component analysis to natural images
Yoshiko Maruyama , Hiroyuki Ito Fac. of Computer Sci. and Eng., Kyoto Sangyo University, Kyoto, Japan
Naofumi Suematsu 1 , Tomoyuki Naito 2 , Hiromichi Sato 2
Yasunobu Igarashi 1 , Takayoshi Aoki 2 , Rui Kimura 3 , Shin Ishii 4
Sch. Eng. Sci., Osaka University, Toyonaka Grad. Sch. Med., Osaka University, Toyonaka
1
Although it is thought that orientation selectivity of visual neurons first emerges at the primary visual cortex, several studies have reported that neurons in the cat lateral geniculate nucleus (LGN) are sensitive to stimulus orientation, especially at high spatial frequency stimuli. In this study, we investigated whether spatiotemporal structures of linear receptive field of LGN neurons can explain their orientation selectivity. First, we measured orientation tunings of LGN neurons with drifting gratings at several spatial frequencies. Next, we clarified the spatiotemporal structures of linear receptive field of the neuron using the reverse correlation technique with dynamic dense white noise stimuli. Then, we computed orientation tunings of the linear receptive field by calculating the convolution of drifting gratings and the linear receptive field. Finally, we compared the measured orientation tunings with predicted tunings from linear receptive field. We found that most LGN neurons exhibited receptive field significantly elongated to the particular orientation consistent with their preferred orientation. In contrast, for a population of neurons, predicted tunings from linear receptive field were significantly broader than measured ones and the preferred orientations of tunings were sometimes significantly different from the measured. Our results suggest that though the elongated linear receptive field may be an essential mechanism for generating orientation tuning in the LGN, the degree of elongation is insufficient to explain entire orientation tunings measured with drifting grating stimuli. We concluded that not only the elongated linear receptive field structure but also some nonlinear mechanisms may contribute to generating sharp orientation tunings observed in the LGN.
Previous experimental studies showed that neurons in the primary visual cortex (V1) have four firing properties to represent visual information. Four firing properties are named luminance gabor, oriented double-opponent, concentric single-opponent, and concentric double-opponent receptive fields. Previous theoretical studies demonstrated that redundancy compressions like independent component analysis (ICA) and sparse coding can derive basic functions corresponding to luminance gabor and oriented double-opponent receptive fields from natural images. On the other hand, emergences of basic functions corresponding to two concentric receptive fields via redundancy compression of natural images have not been reported. In this study, we propose a low pass filtering function of neurons in lateral geniculate nucleus (LGN) is important to derive concentric basic functions in addition to redundancy compression. Neurons in LGN project their axons to neurons in V1. Therefore, it is plausible that LGN contributes to form receptive fields of V1. We show that the concentric double-opponent basis function can be obtained by applying the low pass filtering and Fast ICA to natural images in a computer simulation. However, the concentric single-opponent basis function cannot be not obtained. This reason is thought that the concentric double-opponent basis function functionally includes the concentric singleopponent basis function from the view point of redundancy compression. We also clarify how shapes of basic functions depend on ones of learning images, and how color components of basic functions depend on a color distribution of learning images.
1
doi:10.1016/j.neures.2010.07.1692
2
National Center for Neurology and Psychiatry 2 Nara Institute of Science and Technology 3 RIKEN Brain Science Institute 4 Kyoto University
doi:10.1016/j.neures.2010.07.1694
Abstracts / Neuroscience Research 68S (2010) e335–e446
features defined by correlations (2) and by powers and correlations (3) outperformed those by powers (1). The results suggest that temporal patterns of ECoG signals carry information on visual objects for specific categories.
P3-h27 Functional properties of neurons in the cat posterior, medial lateral-suprasylvian area Kota S. Sasaki 1,2 , Izumi Ohzawa 1,2 1
doi:10.1016/j.neures.2010.07.1690
2
P3-h25 Correlated trial variabilities between single units in the cat visual cortex—Stimulus dependence and its relation with the firing rate tuning
Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan CREST, Japan Science and Technology Agency, Tokyo, Japan
We recorded multiple single units simultaneously from the primary visual cortex of an anesthetized cats. We developed high-density electrode arrays (eight-single electrodes array and four-tetrodes array) fitting to a single hypercolumn. We collected multiple single unit activities over 40 trials under moving bar stimuli of 16 different orientations. We calculated the correlation coefficient (Rsc ) of trial variabilities between simultaneously recorded unit pairs. 64% of unit pairs were found to have statistically significant correlations (N = 324/504, Bootstrap sampling test: P < 0.05). First, we examined whether Rsc reflected similarity of receptive fields of the unit pairs. We defined two signal correlations by the difference of optimal orientations (SCo ) and correlation coefficient between tuning curves (SCm ). Rsc did not show significant dependence on either SCo or SCm . Rsc also didn’t depend on the physical distance of the unit pairs. These independence suggested that Rsc was not likely to originate from common inputs. On the other hand, we confirmed that Rsc of some unit pairs showed significant orientation dependence (N = 49/314, 16%, Kruskal-Wallis test: P < 0.05). To identify the origin of the stimulus dependence, we at first computed correlation coefficient between Rsc and evoked firing rate. For unit pairs having similar optimal orientations (within 90◦ ), only 22% showed significant correlation. In addition, some unit pairs showed significant stimulus dependence of Rsc in spite of the fact that one unit had non-significant rate tuning. Those properties suggest that the origin of firing rate tuning does not necessarily explain stimulus dependence of Rsc .
Motion information is not readily available in retinal images, but must be computed from them along the visual pathway in the brain. Monkeys and cats have several brain areas that are important for motion information processing. To understand how visual information is transformed along the pathway, functional properties of neurons should be compared between different brain areas by using the same sets of stimuli and analyses. We carried out extracellular single unit recordings in PMLS, which receive strong inputs from areas 17/18, of paralyzed and anesthetized cats. The responses of each neuron were examined in the orientation and spatial frequency domain by using a subspace reverse correlation technique with sinusoidal gratings. In addition, to evaluate if the neuron was tuned to a constant speed across different spatial frequencies, its responses were probed by presenting drifting gratings of various spatial and temporal frequencies. These response properties were compared with those of area 17/18 neurons to examine how visual signals are encoded in individual cells in PMLS and transformed after the early stage of visual information processing in the brain. PMLS neurons showed delayed responses compared with area 17/18 neurons (later onset, time to peak and offset than area 17 cells; later onset and time to peak than area 18 cells). With regard to tuning to orientation and spatial frequency, PMLS neurons had similar parameters to area 17 neurons (orientation tuning bandwidth, preferred spatial frequency, spatial frequency tuning bandwidth). However, PMLS neurons had broader tuning bandwidth to orientation and preferred spatial frequency higher than area 18 neurons. A subset of PMLS neurons showed titled response profiles in the joint domain of spatial and temporal frequency, which is a distinct characteristic from area 17/18 neurons. These PMLS neurons were tuned to a constant speed across a range of spatial frequencies.
doi:10.1016/j.neures.2010.07.1691
doi:10.1016/j.neures.2010.07.1693
P3-h26 Relationship between orientation selectivity and spatiotemporal receptive field structure of the cat lateral geniculate neurons
P3-h28 Emergence of concentric double-opponent receptive field properties by applying independent component analysis to natural images
Yoshiko Maruyama , Hiroyuki Ito Fac. of Computer Sci. and Eng., Kyoto Sangyo University, Kyoto, Japan
Naofumi Suematsu 1 , Tomoyuki Naito 2 , Hiromichi Sato 2
Yasunobu Igarashi 1 , Takayoshi Aoki 2 , Rui Kimura 3 , Shin Ishii 4
Sch. Eng. Sci., Osaka University, Toyonaka Grad. Sch. Med., Osaka University, Toyonaka
1
Although it is thought that orientation selectivity of visual neurons first emerges at the primary visual cortex, several studies have reported that neurons in the cat lateral geniculate nucleus (LGN) are sensitive to stimulus orientation, especially at high spatial frequency stimuli. In this study, we investigated whether spatiotemporal structures of linear receptive field of LGN neurons can explain their orientation selectivity. First, we measured orientation tunings of LGN neurons with drifting gratings at several spatial frequencies. Next, we clarified the spatiotemporal structures of linear receptive field of the neuron using the reverse correlation technique with dynamic dense white noise stimuli. Then, we computed orientation tunings of the linear receptive field by calculating the convolution of drifting gratings and the linear receptive field. Finally, we compared the measured orientation tunings with predicted tunings from linear receptive field. We found that most LGN neurons exhibited receptive field significantly elongated to the particular orientation consistent with their preferred orientation. In contrast, for a population of neurons, predicted tunings from linear receptive field were significantly broader than measured ones and the preferred orientations of tunings were sometimes significantly different from the measured. Our results suggest that though the elongated linear receptive field may be an essential mechanism for generating orientation tuning in the LGN, the degree of elongation is insufficient to explain entire orientation tunings measured with drifting grating stimuli. We concluded that not only the elongated linear receptive field structure but also some nonlinear mechanisms may contribute to generating sharp orientation tunings observed in the LGN.
Previous experimental studies showed that neurons in the primary visual cortex (V1) have four firing properties to represent visual information. Four firing properties are named luminance gabor, oriented double-opponent, concentric single-opponent, and concentric double-opponent receptive fields. Previous theoretical studies demonstrated that redundancy compressions like independent component analysis (ICA) and sparse coding can derive basic functions corresponding to luminance gabor and oriented double-opponent receptive fields from natural images. On the other hand, emergences of basic functions corresponding to two concentric receptive fields via redundancy compression of natural images have not been reported. In this study, we propose a low pass filtering function of neurons in lateral geniculate nucleus (LGN) is important to derive concentric basic functions in addition to redundancy compression. Neurons in LGN project their axons to neurons in V1. Therefore, it is plausible that LGN contributes to form receptive fields of V1. We show that the concentric double-opponent basis function can be obtained by applying the low pass filtering and Fast ICA to natural images in a computer simulation. However, the concentric single-opponent basis function cannot be not obtained. This reason is thought that the concentric double-opponent basis function functionally includes the concentric singleopponent basis function from the view point of redundancy compression. We also clarify how shapes of basic functions depend on ones of learning images, and how color components of basic functions depend on a color distribution of learning images.
1
doi:10.1016/j.neures.2010.07.1692
2
National Center for Neurology and Psychiatry 2 Nara Institute of Science and Technology 3 RIKEN Brain Science Institute 4 Kyoto University
doi:10.1016/j.neures.2010.07.1694