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P Downing

Publications and source records attributed to P Downing.

10 recordsLinked to original sources
PubMed2001

Testing cognitive models of visual attention with fMRI and MEG.

Neuroimaging techniques can be used not only to identify the neural substrates of attention, but also to test cognitive theories of attention. Here we consider four classic questions in the psychology of visual attention: (i) Are some 'special' classes of stimuli (e.g. faces) immune to attentional modulation?; (ii) What are the information units on which attention operates?; (iii) How early in stimulus processing are attentional effects observed?; and (iv) Are common mechanisms involved in different modes of attentional selection (e.g. spatial and non-spatial selection)? We describe studies from our laboratory that illustrate the ways in which fMRI and MEG can provide key evidence in answering these questions. A central methodological theme in many of our fMRI studies is the use of analyses in which the activity in certain functionally-defined regions of interest (ROIs) is used to test specific cognitive hypotheses. An analogous sensor-of-interest (SOI) approach is applied to MEG. Our results include: evidence for the modulation of face representations by attention; confirmation of the independent contributions of object-based and location-based selection; evidence for modulation of face representations by non-spatial selection within the first 170 ms of processing; and implication of the intraparietal sulcus in functions general to spatial and non-spatial visual selection.

Attention↗
PubMed1995

Types and tokens unscathed: a reply to Whittlesea, Dorken, and Podrouzek (1995) and Whittlesea and Podrouzek (1995).

N. G. Kanwisher (1987; J. Park & N. G. Kanwisher, 1994) has explained repetition blindness in terms of a distinction in visual perception between type activation and token individuation; repeated items are successfully recognized (matched to stored types) but are less likely than unrepeated items to become individuated as separate perceptual tokens. Whittlesea and colleagues (B. W. A. Whittlesea, M. D. Dorken, & K. W. Podrouzek, 1995; B. W. A. Whittlesea & K. W. Podrouzek, 1995) argued that repetition blindness does not reflect different processing of repeated and unrepeated items but is better explained as the result of a combination of separate but nondistinctive processing of repeated items and postlist report biases. However, we argue that none of the results reported by Whittlesea and colleagues are inconsistent with the token-individuation hypothesis.

Blindness↗
PubMed1992

Anaesthesia and the 'inert' gases with special reference to xenon.

Xenon has many of the properties of the ideal anaesthetic agent and has been proposed as a suitable replacement for nitrous oxide in routine clinical anaesthesia. Xenon, krypton and argon are chemically inert under most circumstances, yet all have anaesthetic properties. Xenon is of particular interest because it is the only 'inert' gas which is an anaesthetic under normobaric conditions. Because of this property, xenon has an important place in the history of the development of theories of anaesthetic action and of concepts such as MAC. Cost is likely to be a major impediment to the regular use of xenon.

Anesthesia, Inhalation↗
PubMed1991

Cyto-histological correlates in a colposcopic clinic: a 1-year prospective study.

As part of the Quality Assurance Program, all surgical pathology reports of cervical colposcopic biopsies, cone biopsies, and hysterectomy specimens of 772 consecutive patients were correlated with cytology results for a period of 1 yr. The abnormality in cytology or histology ranged from HPV effect to invasive carcinoma. Cytohistological correlation within one grade of severity was obtained in 662 (86%) cases. On formal review of the remaining 110 (14%) cases, sampling error occurred in 75 cytology smears and in 21 colposcopic biopsies. Screening and interpretation error occurred in 10 smears and four biopsies. In this study the sensitivity of cervical cytology in detecting epithelial abnormalities was 90%, with a positive predictive value of 99.7%. The false-negative rate of cytology was 11% and the false-positive rate 0.26%. The majority (90%) of false negatives were due to sampling error; the rest were due to laboratory error. The sensitivity of colposcopic biopsy was 97% with a positive predictive value of 99.4%. The false-negative rate of biopsy was 2.7% and the false-positive rate 0.5%. Endocervical cells were seen in 48% (370) of smears and absent in 52% (402). However, in both instances the detection rate of squamous abnormality was 90%. Also 43% (33) of smears that showed endocervical cells failed to contain the abnormal cells. Endocervical curettage or cone biopsy in 16 of these 33 cases clearly showed a small CIN-III lesion high in the endocervical canal. We believe that the value of endocervical cells as an indicator of adequacy is questionable.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Dermoid cyst of the floor of the mouth diagnosed by fine needle aspiration cytology: a case report.

BACKGROUND: Dermoid cyst of the floor of the mouth is a rare, benign lesion requiring surgical intervention. To our knowledge, the preoperative diagnosis of this entity by fine needle aspiration (FNA) cytology has not been previously reported in the cytologic literature. CASE: The patient presented with a massive swelling of the floor of the mouth that displaced the tongue superiorly. A computed tomographic (CT) scan demonstrated a cystic lesion thought to be consistent with a lymphangioma. FNA was performed without complications and demonstrated numerous anucleated and some nucleated squames consistent with a diagnosis of dermoid cyst. Establishment of the correct diagnosis by FNA enabled the surgeon to proceed with the appropriate operation; that outcome might not have been possible had the erroneous CT diagnosis of lymphangioma been trusted. CONCLUSION: A preoperative diagnosis of dermoid cyst of the floor of the mouth was established by FNA. In contrast to reports in the older literature, the FNA procedure caused no complications. In patients presenting with lesions of the floor of the mouth, FNA should be the diagnostic procedure of first choice.

Adult↗
PubMedDate not supplied

Intraoral and transoral fine needle aspiration. A review of 25 cases.

During a four year period, 25 intraoral and transoral fine needle aspirations were performed. The sites aspirated were the parapharyngeal space (7), palate (4), floor of mouth (3), tongue (3) and a variety of other intraoral sites (8). Squamous cell carcinoma, the most common malignancy encountered, was correctly diagnosed in six cases. Other malignancies correctly diagnosed were 2 malignant lymphomas, 1 mucoepidermoid carcinoma and 1 adenoid cystic carcinoma. One malignant case called "carcinoma, probably adenoid cystic carcinoma" proved to be a mucoepidermoid carcinoma. One case called "suspicious for squamous carcinoma" was found to be a branchial cleft cyst. In another case a diagnosis of carcinoma in situ of the tongue was suggested and confirmed by subsequent biopsy, but the underlying adenoid cystic carcinoma was missed. Of seven benign entities, five were correctly diagnosed by fine needle aspiration (FNA), and in three cases the FNA diagnosis was equivocal. Unsatisfactory aspirates were obtained in four cases. Despite some obvious problems, we consider FNA to be especially useful for the evaluation of parapharyngeal masses, which are usually not accessible to routine surgical biopsy, and for palatal masses, which are usually submucosal and therefore often difficult to biopsy.

Biopsy, Needle↗