Perception of the subjective visual vertical (SVV) is mainly based on the contributions from the ... more Perception of the subjective visual vertical (SVV) is mainly based on the contributions from the visual, vestibular, and proprioceptive systems, and participates to the process of spatial orientation in relation to the surrounding environment and to the gravito-inertial force. The SVV can be significantly influenced by the presence of a displaced visual field, as in the case of the rod and frame test (RFT). A series of studies showed the effects of haematic mass shifts to and from the lower limbs on SVV, due to visceral mechanoreceptors (VM) located at the level of the kidneys and of the thorax. These sensors may be artificially activated with a lower body negative pressure (LBNP) device. In this study, the role of visual and VM cues to orientation perception have been evaluated using the RFT and the LBNP devices under a microgravity environment. A preliminary investigation was conducted in a sample of military pilots to develop a RFT protocol to be used in microgravity environments. This protocol was adopted to evaluate the contribution of VM to the SVV in a cosmonaut before, during and after a 10 day space flight, with and without concurrent activation of LBNP. The same test sequence, including LBNP exposure, was repeated a few months later on Earth on the same subject. As expected, the influence of the frame on rod positioning was statistically significant in all test conditions. During the in-flight experimental step, a substantial lack of significant changes compared to the pre-flight condition was observed. Moreover, substantially no effects due to LBNP were observed. A mild rod displacement from the body axis was detected under microgravity compared to the pre-flight recording. Such a finding was in part reduced during LBNP. The same findings were observed during the post-flight repetition of the experiment. Our results showed an absence in this subject of significant effects on the RFT due to microgravity. In conclusion, no effects from his VM on the RFT and minor changes in the SVV could be detected.
Neglect dyslexia is a reading disorder often associated with right-sided brain lesions. In readin... more Neglect dyslexia is a reading disorder often associated with right-sided brain lesions. In reading single words, errors are mostly substitutions or omissions of letters that occupy the left-sided positions. Typically, these errors have been thought to depend on a single mechanism. Conversely, we propose that they are due to different mechanisms. In particular, a visuo-spatial mechanism is responsible for omissions and a perceptual integration process for substitution errors. We measured the performance of six patients with both neglect and neglect dyslexia, analyzing their reading errors as a function of letter spacing. According to our conjecture, letter spacing should increase omissions by moving part of the string further in the unattended space, while it should reduce substitutions by restoring the integration processes. Furthermore, we predict that letter spacing should be more effective with pseudowords compared to words, in that in this latter case lexical effects are supposed to influence attentional and perceptual processes. Accordingly, we found that for pseudowords only the two types of errors are differently affected by this manipulation and only omissions correlate with the severity of the disorder in visuo-spatial tasks.
... Channel for reading. Najib J Majaj najib{at}cns.nyu.edu 1,; Yan Xiang Liang,; Marialuisa Mart... more ... Channel for reading. Najib J Majaj najib{at}cns.nyu.edu 1,; Yan Xiang Liang,; Marialuisa Martelli,; Tracey D Berger and; Denis G Pelli. 1 New York University, USA. Abstract. Letter identification is mediated by just one spatial frequency channel (Solomon & Pelli, 1994). ...
... Channel for reading. Najib J Majaj najib{at}cns.nyu.edu 1,; Yan Xiang Liang,; Marialuisa Mart... more ... Channel for reading. Najib J Majaj najib{at}cns.nyu.edu 1,; Yan Xiang Liang,; Marialuisa Martelli,; Tracey D Berger and; Denis G Pelli. 1 New York University, USA. Abstract. Letter identification is mediated by just one spatial frequency channel (Solomon & Pelli, 1994). ...
Vocal reaction times (RTs) in naming 3- to 8-letter words were measured in proficient and dyslexi... more Vocal reaction times (RTs) in naming 3- to 8-letter words were measured in proficient and dyslexic readers (Study 1). In proficient readers, RTs were independent of word length up to 5-letter words, indicating parallel processing. In the 5- to 8-letter range, RTs increased linearly, indicating sequential processing. Reading experience was associated with both faster discrimination of individual elements and parallel processing of increasingly large word parts. In dyslexics, RTs increased linearly with increasing length indicating reliance on sequential decoding. Individual analysis indicated 2 profiles of RTs (Types A and B). In Study 2, the distinction between A and B dyslexics was not associated with the use of different reading procedures. However, a more marked speed deficit characterized Type B dyslexics.
... Pierluigi Zoccolotti Æ Maria De Luca Æ Gloria Di Filippo Æ Anna Judica Æ Marialuisa Martelli ... more ... Pierluigi Zoccolotti Æ Maria De Luca Æ Gloria Di Filippo Æ Anna Judica Æ Marialuisa Martelli ... languages with more transparent orthography, high levels of reading accuracy are reached quite rapidly (eg, German: Wimmer & Hummer, 1990; Italian: Cossu, Gugliotta, & Marshall ...
Verghese and Stone (1995) showed that reducing the perceived number of objects by grouping also r... more Verghese and Stone (1995) showed that reducing the perceived number of objects by grouping also reduces objective performance. Shams, Kamitani, and Shimojo (2000) showed that a single flash accompanied by multiple beeps appears to flash more than once. We show that objective orientation-discrimination performance depends solely on the perceived number of flashes, independent of the actual number of beeps and flashes. Thus the unit of perceptual analysis seems to be a perceived event, independent of how it is induced.
Perception of the subjective visual vertical (SVV) is mainly based on the contributions from the ... more Perception of the subjective visual vertical (SVV) is mainly based on the contributions from the visual, vestibular, and proprioceptive systems, and participates to the process of spatial orientation in relation to the surrounding environment and to the gravito-inertial force. The SVV can be significantly influenced by the presence of a displaced visual field, as in the case of the rod and frame test (RFT). A series of studies showed the effects of haematic mass shifts to and from the lower limbs on SVV, due to visceral mechanoreceptors (VM) located at the level of the kidneys and of the thorax. These sensors may be artificially activated with a lower body negative pressure (LBNP) device. In this study, the role of visual and VM cues to orientation perception have been evaluated using the RFT and the LBNP devices under a microgravity environment. A preliminary investigation was conducted in a sample of military pilots to develop a RFT protocol to be used in microgravity environments. This protocol was adopted to evaluate the contribution of VM to the SVV in a cosmonaut before, during and after a 10 day space flight, with and without concurrent activation of LBNP. The same test sequence, including LBNP exposure, was repeated a few months later on Earth on the same subject. As expected, the influence of the frame on rod positioning was statistically significant in all test conditions. During the in-flight experimental step, a substantial lack of significant changes compared to the pre-flight condition was observed. Moreover, substantially no effects due to LBNP were observed. A mild rod displacement from the body axis was detected under microgravity compared to the pre-flight recording. Such a finding was in part reduced during LBNP. The same findings were observed during the post-flight repetition of the experiment. Our results showed an absence in this subject of significant effects on the RFT due to microgravity. In conclusion, no effects from his VM on the RFT and minor changes in the SVV could be detected.
Neglect dyslexia is a reading disorder often associated with right-sided brain lesions. In readin... more Neglect dyslexia is a reading disorder often associated with right-sided brain lesions. In reading single words, errors are mostly substitutions or omissions of letters that occupy the left-sided positions. Typically, these errors have been thought to depend on a single mechanism. Conversely, we propose that they are due to different mechanisms. In particular, a visuo-spatial mechanism is responsible for omissions and a perceptual integration process for substitution errors. We measured the performance of six patients with both neglect and neglect dyslexia, analyzing their reading errors as a function of letter spacing. According to our conjecture, letter spacing should increase omissions by moving part of the string further in the unattended space, while it should reduce substitutions by restoring the integration processes. Furthermore, we predict that letter spacing should be more effective with pseudowords compared to words, in that in this latter case lexical effects are supposed to influence attentional and perceptual processes. Accordingly, we found that for pseudowords only the two types of errors are differently affected by this manipulation and only omissions correlate with the severity of the disorder in visuo-spatial tasks.
... Channel for reading. Najib J Majaj najib{at}cns.nyu.edu 1,; Yan Xiang Liang,; Marialuisa Mart... more ... Channel for reading. Najib J Majaj najib{at}cns.nyu.edu 1,; Yan Xiang Liang,; Marialuisa Martelli,; Tracey D Berger and; Denis G Pelli. 1 New York University, USA. Abstract. Letter identification is mediated by just one spatial frequency channel (Solomon & Pelli, 1994). ...
... Channel for reading. Najib J Majaj najib{at}cns.nyu.edu 1,; Yan Xiang Liang,; Marialuisa Mart... more ... Channel for reading. Najib J Majaj najib{at}cns.nyu.edu 1,; Yan Xiang Liang,; Marialuisa Martelli,; Tracey D Berger and; Denis G Pelli. 1 New York University, USA. Abstract. Letter identification is mediated by just one spatial frequency channel (Solomon & Pelli, 1994). ...
Vocal reaction times (RTs) in naming 3- to 8-letter words were measured in proficient and dyslexi... more Vocal reaction times (RTs) in naming 3- to 8-letter words were measured in proficient and dyslexic readers (Study 1). In proficient readers, RTs were independent of word length up to 5-letter words, indicating parallel processing. In the 5- to 8-letter range, RTs increased linearly, indicating sequential processing. Reading experience was associated with both faster discrimination of individual elements and parallel processing of increasingly large word parts. In dyslexics, RTs increased linearly with increasing length indicating reliance on sequential decoding. Individual analysis indicated 2 profiles of RTs (Types A and B). In Study 2, the distinction between A and B dyslexics was not associated with the use of different reading procedures. However, a more marked speed deficit characterized Type B dyslexics.
... Pierluigi Zoccolotti Æ Maria De Luca Æ Gloria Di Filippo Æ Anna Judica Æ Marialuisa Martelli ... more ... Pierluigi Zoccolotti Æ Maria De Luca Æ Gloria Di Filippo Æ Anna Judica Æ Marialuisa Martelli ... languages with more transparent orthography, high levels of reading accuracy are reached quite rapidly (eg, German: Wimmer & Hummer, 1990; Italian: Cossu, Gugliotta, & Marshall ...
Verghese and Stone (1995) showed that reducing the perceived number of objects by grouping also r... more Verghese and Stone (1995) showed that reducing the perceived number of objects by grouping also reduces objective performance. Shams, Kamitani, and Shimojo (2000) showed that a single flash accompanied by multiple beeps appears to flash more than once. We show that objective orientation-discrimination performance depends solely on the perceived number of flashes, independent of the actual number of beeps and flashes. Thus the unit of perceptual analysis seems to be a perceived event, independent of how it is induced.
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