Neuropsychologm, Vol 27, No. 4. pp 471483, 1989 Prmted m Great Britain.

W28~ 3932,89 S3 OO+OoO c 1989 Pergamon Press plc

ATTENTION AND INTERFERENCE IN THE PROCESSING OF GLOBAL AND LOCAL INFORMATION: EFFECTS OF

UNILATERAL TEMPORAL-PARIETAL JUNCTION LESIONS

MARVIN R. LAMB,*? LYNN C. ROBERTSON? and ROBERT T. KNIGHT:

tDepartments of Psychiatry and :Neurology, University of California, Davis, Veterans Administration Medical Center, Martinez, California, U.S.A.

(Received 2 February 1988; accepted 1 June 1988)

Abstract-The processing of hierarchical stimuli was examined in patients with lesions in the temporal-parietal junction. In separate blocks of trials, subjects were instructed to identify the letter at the local or the global level of a hierarchical stimulus. Consistent with previous findings, reaction times for controls were faster in the globally than in the locally directed condition and reaction times to the local level were longer when the letters at the two levels were different (e.g. local “S’s forming a global “H”) than when they were the same (e.g. local “S’s forming a global “S”). In other words. controls exhibited interference when locally directed. Patients with lesions centered in the rostra] inferior parietal lobe (IPL) showed interference effects similar to controls. In contrast; patients with lesions centered in the posterior superior temporal gyrus and adjacent caudal inferior parietal lobe (STG) showed no interference. The data suggest that the posterior superior temporal plane and adjacent caudal inferior parietal lobe plays an important role in the integration ofand/or attention to local and global level information.

INTRODUCTION

THE TEMPORAL-parietal junction serves an important role in the processing of visual stimuli, especially with respect to spatial analysis. For example, single units in area 7 of the monkey respond to task relevant visual targets independent of eye movements [S, 22, 26, 391 and destruction of area 7 produces deficits in perceiving the spatial relations between stimuli but not in perceiving other properties such as shape, hue, or brightness [28,38]. This region in monkeys (i.e. area 7) is generally thought to correspond to the inferior parietal lobe of humans (areas 39 and 40) [l]. Although the role of the posterior superior temporal gyrus (area 22) in visual perception has not been as well studied, recent anatomical evidence of projections to area 22 from visual area MT [lo, 371 and from the inferior parietal lobe [35] suggests that this area may well be involved in both perceptual and attentional mechanisms. Studies in humans with temporal-parietal lesions have further documented the role of this area in visual perception [2, 3, 9, 14, 25, 31, 321.

Damage to the temporal-parietal junction in humans also affects mechanisms involved in the processing of hierarchically organized patterns [13, 341. Hierarchical organization simply means that there are smaller patterns or objects subsumed within larger patterns or objects. A door, for example, might be considered a whole object and the doorknob a part of

*Correspondence to be addressed to: Marvin R. Lamb, Research 151, Veterans Administration Medical Center, 150 Muir Road, Martinez, CA 94553, U.S.A.

471

417 M~KVIN R. LAMB. LYNN C. RO~SLKTSOI and ROBI:KI T. K~I(;HI

that whole. However, the door would also be a part in the context of a house. Parts and wholes are therefore defined by their relative place in a hierarchy of levels going from more local to more global. This conceptualization is appealing, not only because it provides an unambiguous definition of “parts” and “wholes”, but also because evidence suggests that this is one way the perceptual system actually parses visual scenes [8, 13. 33. 341.

Findings from cognitive psychology have shown that perceptual and attentional mechanisms interact to determine whether local or global forms are processed first and further that the level processed first interferes with the processing of the other level [ZO, 24. 27,291. This interference is automatic in thd sense that the first level cannot be ignored even when it is irrelevant for the task. However, we have recently presented data that speed of processing and interference may vary independently in normals suggesting that the two effects depend on different mechanisms 1201. In addition, pilot data from a different study in our laboratory also suggested that interference could be reduced in patients with posterior superior temporal gyrus lesions without accompanying changes in relative speed of processing. The present study examines this possibility directly.

A reaction time task similar to one employed in normals [20. 23, 24, 261 was used to examine (a) the relative speed with which local and global forms could be identified and (b) the degree to which the form at one level interfered with a response to the form at the other level. Stimuli like that shown in Fig. 1 were presented in the left visual field, center, or right visual field. In separate blocks of trials subjects were directed to identify the letter at either the local or the global level as quickly as possible. Within this paradigm relative speed of processing is measured as the difference in time taken to identify letters at the local vs the global levels.

HHHH H HHHH

H HHHH FIG. I. An example of a hierarchical stimulus in which local “H”s form a global “S’

Interference is measured as an increase in reaction time at a given level when the patterns at the two levels are different (e.g. local “S”s forming a global “H”) compared to when the patterns at the two levels are the same (e.g. local “S’s forming a global “S”).

METHOD

The average age of the control subjects was 50.3 (SD= 13.23). and the avcragc age of the patlent\ was 52.1 (SD = 11.14). The patients were all selected on the basis of evidcncc of a single focal lesion in the temporal-parielal region. There were 10 control subjects, 7 subjects with lesions centered in the rostra1 inferior parietal lobe (IPL). and 6 subjects with lesions centered in the superior temporal gyrus and adjacent caudal inferior parietal lobe (STG 1. The clinical specifications for each patient as well as the location and extent of lesions, visual acuity and field deficits are presented in Table 1. All patients were male except for one female (K.E.). Ten subjects had suffered stroke. one I PL

subject (K.E.) had had tumor excision, but had been stable for over 5 yr with no evtdence of tumor regrowth, one IPL subject (M.K.) had received a shrapnel wound in Vietnam, and one STG subject (G.B.) had sustained head trauma requiring a surgical debridement of the right temporal-parietal region. Subjects were scrcencd for drug and alcohol addiction, dementia, psychiatric disorder, marked aphasia and major medical dlness independent of their neurological problems. Patients with evidence of increased intracranial pressure or shift of midline structures were excluded. All subjects had normal orcorrected to near normal visual acuity as measured by Snellen chart. One STG subject (H.H.) had evidence of mild neglect as measured by Albert’s line crossing test. Details of the occurrence 01 neglect during the onset of neurological problems were unknown. Visual fields were tested by confrontation and defects are noted in Table 1. One IPL subject (E.S.) showed a partial quadranopsia in the lower right quadrant of both eyes and one STG subject (R.W.) showed a similar lower right quadranopsia and an additional central scotoma in the right eye.

Because the patients were also being run in auditory experiments in a different laboratory, they were screened for hearing loss, and no subject had evidence of significant hearing difhculty. No subjects exhibited evidence of hemiparesis. All subjects were at least I yr post insult in order to optimize baseline stability. All of the STG subjects wtth left hemisphere damage and one of the IPL subjects (F.O.) with left hemisphere damage showed mild IO moderate signs of aphasia upon neurological examination. Another IPL subject (F.A.) had suffered a transient episode of aphasia post insult but no longer exhibited any evidence of aphasia. The rest of the subjects had ncvcr shown evidence of aphasia.

The 10 normal control subjects were sex and age matched to the patient groups They all had normal or corrected to normal vision. Both controls and patients were paid for their participation.

Lrsion location

Lesion location was verified by CT scan in all patients. Location was judged by three independent raters. two of whom were naive to the hypotheses of the present study, and agreed upon areas were reconstructed by a neurologist (R.T.K.) onto axial templates drawn from an atlas 171. Individual and group lateral reconstructions were then computed from the axial sections [It]. Figure 2 shows the average axial reconstruction of the two brain damaged groups. One IPL patient (F.O.) had minimal lesion extension into the posterior superior temporal plane, and moat STG patients had lesions extending into caudal IPL. The STG and IPL patient subgroups were thus anatomically differentiated on the basis of involvement of posterior area 22. A second criterion for inclusion in one group or the other was on the basis ofelectrophysiological data. Two patients (R.G. and G.B.) produced too much noise due to muscle movements, and their electrophysiological data were unavailable. However, inspection ofTable I shows that these cases were not ambiguous in terms of the anatomy involved. All other STG patients had reduced or absent auditory evoked potentials generated by superior temporal plane structures [17]‘as well as reductions of the assumed cognitive P300 potential [IS]. IPL patients had normal temporal components and P300 potentials but reduced N200 responses. F.O. was a special anatomical case. Although area 22 was partially involved on the basis of CT reading, his auditory temporal components were normal upon electrophysiological recording. The average lesion volume was 51.0 cc for IPL and 40.7 cc for STG.

Apparatus and .srimuli

The stimuli were generated on a Princeton Graphics SR-I 2 monitor controlled by an IBM PC-XT computer with Sigma Designs Graphic Dazzler I and Enhancer cards. All stimulus events were white on a dark surround. Stimulus timing (onset, offset, and duration) was tied to the vertical sync pulse. All other events (responses, ITI, etc) were timed using the 8253 chip set to a 1 msec time base. The status of the response keys was monitored via the game port.

A small square presented in the center of the monitor served as the fixation point. It subtended approx. 0.21 visual angle. A set of hierarchically formed stimuli was also used. Figure I shows an example ofsuch a stimulus with the letter “S” at the global level and the letter “H” at the local level. Large letters were constructed from the appropriate placement ofsmall letters in a four (horizontal) by five (vertical) matrix. Small letterssubtended approx. 0.64-’ visual angle vertically and 0.42’ horizontally. Large letters subtended about 3.6’ visual angle vertically and 2.3 horizontally.

The letters “H” and “S” served as targets. In the Consistent condition, the same letter appeared at the local and global levels (i.e. both local and global letters were “H” or both were “S”). In the Inconsistent condition. the local and global letters were different (i.e. global “H” and local “S” or global “S” and local “H”). In the Single condition, the stimulus was either (a) one small letter presented alone or (b) a large letter composed of small “0”s.

PiWCdUiY

Subjects sat with their head resting against the back of an easy chair. The distance between their eyes and the CRT screen was approx. 54 cm. A 500 msec tone announced the beginning of each trial. The tone was followed, after 100 msec, by a 500 msec presentation of the central fixation point. Subjects were instructed to look directly at the fixation point and not to move their eyes. These instructions were repeated between each block oftrials. The fixation point was followed immediately by a 100 msec presentation of one of the stimulus patterns. The stimulus pattern appeared randomly and equally often in the left, center, or right portion of the screen. Peripheral stimuli appeared 2.7” of visual angle out from the fixation point, measured to the inner edge of the stimulus pattern. Subjects had

474 MAKWN R. LAMH. LYNN C. ROHEKTSON and ROHEKT T. KNIGHT

ATTENTION AND INTEKFERENCE 47s

e -

MAKVIN R. LAMB. LYNV C. RO~ER~SO~S and ROHI;KT T. KNIGIIT

ci

ATTENTION AND INTERFEKEN(‘t 477

3000 msec in which to respond. A 1000 msec intertrial interval followed either a response or the 3000 mscc interval. whichever came first.

Stimuli were presented in four blocks oftrials, 324 trials in all. Each block began with 9 warm-up trials which were not included in the analysis. In the locally directed condition the small letters served as the targets and in the globally directed condition the large letter served as the target. Subjects indicated the identity of the target (“H” or “S”) by pressing one of two keys. Subjects were directed globally for Blocks 1 and 2 and locally for Blocks 3 and 4, or vice versa. This sequence was counterbalanced between subjects. There were 99 trials tn Blocks I and 3 and 63 trials in Blocks 2 and 4.

Before data collection began. subjects received a block of 18 globally directed practtce trials and a block of IX locally directed practice trials. Before each block, both practice and data, subjects were directed to the relevant level and given comprehension trials in which hierarchical stimuli were presented in the center of the screen one at a time. remaining on the screen until the subject made a correct response. Subjects received at least 16 comprehension trials before each block. but continued until it was clear that the response rule was understood. The order in which the glohally~locally directed conditions were presented was the same for the practice and data trials for any given subject. Target letter (“H” and “S”), consistency condition (Consistent. Inconsistent. and Single). and location (Left. Center, and Right) were completely counterbalanced within each block. Stimuli were presented randomly with the restrictions that the target could not he the same letter, or appear in the same location on more than four consccutivc trials.

Patients always used the hand ipsilateral to their lesion to respond. Four of the control subjects used their right hand and six used their left, a ratio chosen to match as closely as possible that in the brain damaged groups. Subjects using their right hand pressed the “H” key with their mdex finger and the “S” key with their middle finger. Subjects using their left hand used the opposite fingers for the “H” and “S” responses. All subjects were instructed to respond as quickly as possible while keeping errors to a minimum. Reaction time (measured from stimulus pattern onset to key closure) and errors were recorded.

RESULTS

Reaction times were analyzed using an analysis of variance (ANOVA) for mixed designs with Group (control, IPL, and STG) as the between subjects factor and Level (local vs global), Consistency (consistent, single, or inconsistent), and Field (contralateral, middle, or ipsilateral) as within subjects factors. Median reaction times were calculated for each cell in the design for each subject, and the data reported are means of those medians. The data for each individual subject are presented in Table 2.

The overall ANOVA revealed that the data replicated the literature on hierarchical stimulus processing in normals [20, 24, 27, 291. Reaction times were faster when subjects were directed globally than when they were directed locally, F (1, 20) = 4 1.32, P < 0.00 1, and this difference in speed of processing for local and global targets was greater for peripherally than for centrally presented stimuli, F (2,40) = 8.67, P < 0.001. Reaction times were also faster in the consistent and single conditions than in the inconsistent condition, F (2, 40) = 6.07, P-c 0.01, especially when subjects were directed locally F (2, 40) = 3.24, P<O.O.5. Like the difference in speed of processing, these interference effects were also more pronounced for peripheral than for central presentation, F (4, 80) = 10.77, P-c 0.001 .*

However, as can be seen in Fig. 3, the pattern of results was not the same for the three groups. This difference was reflected in two significant Group interactions. Both the Group x Level x Consistency, F (4, 40) = 3.52, P < 0.05, and the Group x Level x Consis- tency Field, F (8, 80)=2.81, P<O.Ol, interactions were significant. Differences in the pattern of responses for the STG group were the source of these interactions. When the data from

*The single condition was included in the present experiment as a control for the difference tn size between local and global letters. That is, performance might differ in the locally vs globally directed conditions because letters 31 the local level are smaller than letters at the global level rather than because of their relative positions in the hierarchy. As expected, the single condition reaction times were faster for small than for large letters suggesting that size per se did have some effect, F (1,9) = 14.36, P <O.Ol. Since this difference did not differ for the three groups the single condition will not he discussed in detail. For a more thorough discussion see LAMB and ROBEKTSO~ 1201.

418 MAKVIN R. LAMH, LYNN C. R~LEKTSUN and ROBERT T. KNSHT

Table 2. Median reaction times (msec) for all brain damaged subjects

Contralateral Middle Ipsilateral c s I c s I c S I

IPL (Lq/t ) R.G.

E.S.

F.O.

F.A.

M.K.

IPL (Riyht ) K.E.

R.R.

STG (Lr/r) R.W.

D.L.

L.G.

B.B.

STG (Right) G.B.

H.H.

Local 444 592 Global 422 45X Local 1214 1415

Global X46 832 Local x39 64X

Global 559 563 Local 735 709

Global 557 516 Local 644 692

Global 583 615

x04 496 549 461 419 466

12X3 1094 1167 842 957 749 94x 663 712 615 547 551 855 649 683 478 568 532 748 651 733 670 590 630

Local 897 848 817 632 682 Global 596 615 604 559 604 Local 680 630 740 564 822

Global 574 596 568 552 546

Local Global Local

Global Local

Global Local

Global

86X 514 482 487 834 892 772 800 X26 1014 609 645

1516 I967 I366 1 x54

758 589 601 510 417 545 836 922 194 840 712 738 973 742 779 689 471 hX1

I598 1902 2326 I667 1512 1935

Local Global Local

Global

744 719 743 703 712 747 79x 766 67X 712 762 718

638 623 627 599 630 64X 722 755

553 475 478 463

1232 1167 808 747 706 756 5x2 614 X60 653 554 55x 618 752 630 68X

647 760 671 611 638 679 618 553

513 718 409 409

1222 I343 777 831 682 X13 593 551 X26 863 510 551 684 821 752 632

741 858 656 636 594 XIX 561 590

656 719 590 XII 530 503 456 469 955 x21 735 885 771 769 715 770 855 944 782 747 800 677 635 626

1748 2284 2161 I725 1488 1997 I576 1558

653 611 737 76X 685 620 675 684 663 620 604 692 806 699 650 703

just the control and IPL groups were compared, these two Group interactions were not significant (Fs< 1.0) whereas both were significant when control and STG subjects were compared, F(2, 28)=4.19, P<O.O5, for the Group x Level x Consistency and, F (4, 56) = 5.98, P< 0.001, for the Group x Level x Consistency x Field.

The Group interactions reflect the fact that, unlike control and IPL subjects, STG subjects showed no interference at the local level for peripherally presented stimuli. Both control and IPL subjects showed a significant global level advantage, F (1,9)= 35.76, P<O.OOl, for control and, F (1, 6)= 17.32, PcO.01, for IPL, which was more pronounced in the inconsistent than consistent conditions, F(2, 18)=4.72, PcO.05, for control nnd F (2, 12)= 5.03, PcO.05, for IPL. Furthermore, this Level x Consistency effect changed across field for both controls, F (4, 36) = 20.60, P < 0.001. and IPL patients, F (4,24) = 3.13, PcO.05, but not for STG patients. Thus, the measure of interference (a difference between consistent and inconsistent conditions) was greater in the periphery than in the middle for the control and IPL groups, but there was no interference in any field for the STG group. There was only one significant effect for the STG group which was a main effect of Level, F(I. 5)=6.35, P<O.O5.

It should be noted that the functions depicted in Fig. 3C makes it appear as though STG subjects were much slower overall than all the other subjects, but in fact there was no significant main effect of Group in the overall reaction time. As can be seen in Table 2, the

1100

CONTROLS (N-10)

1000-- A LOCAL . GLOBAL

WO--

,00__

600__

500 , I I I I I I I I C S I c

1 I S I C S I

LEFT HIDDLE RIGHT

1100

1000

900

800

100

600

500

1100

--

r C S I

CONTRAulEIlAL

IPL (N-7)

C S I C S I

MDDLE IPSIIATERAL

t

STC (N-6)

1 I I I I I I I

C S I C S I C S I

CONTRALATERAL t4IDDLE IPSIIATERAL

FIG. 3. Reaction times for locally (triangles) and globally (circles) directed trials as a function of consistency (C = consistent condition, S = single condition, I = inconsistent condition) for stimuli presented in the various

locations for each group.

480 MAKLIN R. LAMH, LVNY C. ROHFKTSON and ROHFKT T. KNIGHT

apparent increase in reaction time for the STG group was due to the data of a single subject (BB). It is not clear why this subject’s data were different. However, the pattern of statistical findings were the same whether the data from this subject were included in the analysis or not. Thus this subject’s data are not solely responsible for the effects reported here.

One final point deserves mention. While the present experiment was primarily concerned with intrahemispheric differences in hierarchical stimulus processing, many studies have reported interhemispheric differences, the left hemisphere being associated with the processing of local forms and the right with global. A comparison of subjects with left vs right hemisphere damage (data collapsed over IPL and STG) revealed that left hemisphere damaged subjects showed a significantly greater global advantage than controls, F (1, 17) = 10.22, P < 0.01, while right hemisphere subjects did not, although the means were in the expected direction. This is consistent with previous findings 14, 8, 33, 341.

The error rate for all three groups was low (Mean = 2.9,9.6, and 7.9% for control, IPL and STG subjects respectively) and when reaction time and errors were compared there was no indication of a speed-accuracy tradeoff (r = + 0.89, r = + 0.90, and r = + 0.50 for control, I PL. and STG subjects respectively). A speed accuracy tradeoff (i.e. a negative correlation between reaction time and errors) would indicate that variations in reaction time could be attributed to a simple criterion or strategy shift.

DISCUSSION

STG patients showed no interference between global and local levels while IPL patients showed normal interference effects (i.e. faster reaction times in the consistent than in the inconsistent condition). This occurred in the absence of a change in the relative speed of processing ofglobal and local levels (i.e. the difference in reaction time between responding to global and local targets did not change). Thus the normal interaction of information between the global and local levels did not occur for STG subjects while the relative speed of processing was normal. It is interesting that, in a sense, STG subjects actually performed better than controls since processing at the two levels occurred without producing interference. However, it seems likely that this apparent benefit results from certain demands made by the present task and would not occur under different conditions. For example, the present task requires that subjects respond to one level while ignoring the other. Thus a lesion which results in reduced integration of information from the two levels would facilitate performance on this task. In contrast, such a lesion would prove quite deleterious to performance on a task which required subjects to integrate information from the two levels into a coherent unit. It is not clear at the present time exactly what the nature of the integration process might be. It is interesting to note. however, that the lesions in the STG group lie adjacent to and are anatomically connected to pathways that have been shown in monkeys to be important for stimulus identification [38].

A different explanation of the performance of the STG subjects is suggested by an experiment conducted by KNIGHT et trl. [18]. In their experiment, most of the same subjects that participated in the present experiment responded manually to a 1500 Hz target tone which occurred occasionally among presentations of a 1000 Hz standard tone. There were also infrequent presentations of various novel sounds, including both computer generated complex tcnes and unexpected environmental sounds. Electroencephalographic recordings from normals showed that the novel sounds elicited a P-300 potential (a positive potential appearing about 300 msec following the eliciting stimulus). While the meaning of this

ATTENTION AND INTEKFEKENCE 4x1

potential is controversial, some evidence suggests that a P-300 generated in response to unexpected visual or auditory stimuli is associated with the orienting of attention to relevant or potentially relevant stimuli in the environment [6, 161. KNIGHT et al. [IS] demonstrated that subjects with lesions centered in the STG showed reduced or absent P-300 potentials to the novel stimuli. That is, unlike controls or patients with IPL lesions, they showed no electrophysiological evidence of being distracted by a potentially relevant novel auditory stimulus. Similarly, subjects in the present experiment showed no evidence of being distracted by visual stimuli at the currently unattended (but potentially relevant) level in a selective attention task. This suggests the possibility that structures in the posterior superior temporal plane play a role in an amodal attentional mechanism responsible for alerting the system to potentially relevant events.

The automatic “alerting” or “orienting” mechanism proposed here can also be discriminated from a different controlled attentional mechanism which also affects hierarchical stimulus processing. Several investigators have shown that the relative advantage between global and local levels can be reversed by manipulations intended to change the allocation of attention to those levels [15, 19, 341. These studies point to the existence of a controlled process which distributes attention between the two levels according to task demands. In a recent study by ROBERTSON et al. [34], many of the same subjects who participated in the present study searched for a target letter which occurred at one or the other level of a hierarchical stimulus in a divided attention task. STG subjects showed evidence of a normal ability to control attention, while IPL subjects showed evidence supporting an inability to control the allocation ofattention. This result is consistent with the growing body of evidence demonstrating that structures in the IPL play a role in spatial attention [12, 21, 22, 303 and further demonstrates that the rostra1 IPL is an important region for the controlled attentional mechanism which can influence the relative speed with which local and global information is processed. This controlled attentional process should be contrasted with the hypothesized automatic alerting or orientation mechanism which the present data suggest might be associated with the superior temporal gyrus and adjacent caudal inferior parietal lobe.

It should also be noted that the present findings are consistent with a growing body of evidence that there are hemisphere specific mechanisms differing in the efficiency with which local and global level information are processed [S, 23, 33, 34, 361. Subjects with left hemisphere lesions (both IPL and STG) showed a larger global advantage than controls while subjects with right hemisphere lesions did not.

In sum, the present data indicate that interference between the local and global levels occurs as the result of the operation of a mechanism associated with neural structures centered in the posterior superior temporal plane and adjacent caudal IPL. In addition, the findings are consistent with other data that have shown that local information is processed more efficiently in the left and global information in the right hemisphere. As in our previous study with normals [20], the interference effects occurred independently of the changes in the relative speed of processing at the two levels. This is rather convincing evidence that the interhemispheric mechanism/s responsible for changes in the speed of processing of the local and global levels is independent of the intrahemispheric mechanism/s responsible for producing interference between levels. This is in contrast to theories of perceptual organization proposed by cognitive psychologists which have assumed interference to be a direct function of the relative speed with which global and local levels are processed. We have shown, both in normals and in brain damaged patients, that this need not be the case.

482 MI\KVIU R. LAMB. LYN’U‘ C. RONKISON and ROHEKT T. KNIC;H,I

4~,~,1o~\/rtl~c,r,1rrzr\~~The present work was supported by the Medical Research Service of the Veterans Administration. NIAAA grants AA06486 and to LCR, and by NINCDS grant NS21135 to RTK. We wish to thank Clay Clayworth. Robert Frey. Greg Shenaut. and David Woods for development of the CT scan reconstructIon algorithms.

REFERENCES I. AIUIIFKSON. R. A. lnfcrior parietal lobule function in spatial perception and visuomotor integration. In

Ifc~ndhr>& q/ Ph?sio/oy,v. F. PLUM (Editor), Vol. V, Part 2. Waverley Press, Baltimore, Maryland, 1987. 2. BENSOU. D. F.. SEC;AKKA, J. and ALREKT, M. L. Visual agnosia-prosopagnosia. Archs Neural. 30,307 3 IO. 1974. 3. B~.TTTKS. N., SOI:LL)NI:K. C. and FEI~O, P. Comparison of parietal and frontal lobe spatial deficits in man:

extrapersonal vs personal (egocentric) space. Percept. Motor Skills 34, 27-34, 1972. 4. BKAUSHA~. J. L. and NET~L~TON. N. C. The nature of hemispheric specialization in man. Rehm Bruin S?i. 4,

51 91.1981. 5. BUSHNIU. M. C.. GOLI)B~KG, M. E. and ROLIINSON. D. L. Behavioral enhancement of visual responses in

monkey cerebral cortex. 1. Modulation in posterior pa&al cortex related to selective visual attention. ./. &‘carophy.sio/. 46, 755 772. 1981.

6. COUK(‘HESU. E.. HII.LYAKU, S. A. and GALAMHOS, R. Stimulus novelty, task relevance and the visual evoked potential in man. Elrctrocncrph. C’lin. .Yrurophysiol. 39, 131 143, 1975.

7. DEAKMONI), S. J., F~:sco, M. M. and DEWEY. M. M. Sfructurr offhe Humun Brain. Oxford Umversity Press, New York, 1976.

8. DELIS, D. C.. Rost~rso~, L. C. and EFKON. R. Hemispheric specialization of memory for visual hierarchlcai stimuli. N~urop.sy~ho/~,yicr 24, 205 2 14, 19X6.

9. DF RTNZI. E. and FAGLIONI. P. The relationship between visuo-spatial impairment and constructional apraxia. Corrc~.u 3, 327 342. 1967.

IO. DESIMONF, R. and IJN(ZKL~IUEK. L. G. Multiple visual areas in the caudal superior temporal ~ulcus of the macaque. J. Conlp. Neurd. 248, I64 189, 1986.

1 I. FKI.Y. R. T., Wooos. D L.. KNIC;Hr, R. T.. SCAI~NI. D. and CLAYWOKTH, C. C. Defining functional arcas with averaged CT scans. SK. Nmrosci. Ahsrr. lYX7.

12. ~oLLu3CKG, M. E. Moving and attending in visual space: single ccl1 mechanisms in the monhey. In Sputirrl Abilities: 0rwlopmrntcll NN/ fhwiolo~/icn/ Foundu~ims. M. POTE(;AL (Editor). Academic Press, New York. 19x2.

13. HLMPHKEYS. G. W.. R~u~>ocfi. J. and QI;INLAN, 1’. T. Interactive processes in perceptual organization: evidence from visual agnosia. In ,4ttrrztiorr NU/ PUfornrcrncr XL. M. I. POSNEK and 0. S. M. MAKIN (Editors). Erlbaurn. Hillsdale, New Jersey, 1985.

14. KIhfCK.4. D. Right temporal lobe damage. Archs Nruroi. 8, 264 271, 1963. 15. KINU~~A, R. A.. Sous-MAULS. V. and HO~~MAY. J. Attending to different levels ofstructurc in a visual image.

Prrwpl. Ps~chophys. 33, 1 10, 1983. 16. KNIGHT. R. T. Decreased response to novel stimuli after prefrontal lesions in man. Elr~~trocwwph. c,/in.

Nrurophysiol. 54, 9 20. 1984. 17. K%I~;II~. R. T., S(‘ABINI. D., WOOLS. D. L.. and CLAYWOKTH. C. C. Effects of temporal and parietal lesions on

temporal components of the human auditory evoked potential. Sot. Neurosci. (Ahstr.) 13, 331, 1987~1. IX. KNIGHT. R. T.. S~,\I<INI. D., Wooos, D. L. and CLAvwoKrH, C. C. Differential effects of par&al or

temporal parietal lesions on human NZOO and P300. ~Vcwrtwi. (Ahstr.) Suppl. Lb/. 22, 521, 1987b. 19. LAMH. M. R. and ROUEKTSON. L. C. Effect of actute alcohol on attention and the processing of hierarchical

patterns. .4/01hol.: C/in. E.Yp. Res. 11, 243 248. 1987. 20. LAMB, M. R. and ROHEKTSON, L. C. The processing of hierarchical stimuli: effects of retinal locus, locational

uncertainty. and stimulus identity. Puwrpr. Fsydwphys. 44, 172 181. 19xX. ?I. LYNCH. .I. C. The functional organization ofposterior parietal association cortex. H&w. Bruin Sci. 3,485 534,

1980. 22. LYMX. J. C.. MOUNTCAS~L~, V. B.. TALBOT. W. H. and YIN, T. C. T. Directed visual attention. J. Nauwphysiol.

40, 361--3X9, 1977. 23. MAKTIV. M. Hemispheric specialization for local and global processing. Neurops~chologict 17, 33 40, 1979a. 24. MAKTIN, M. Local and global processing: the role of sparsity. Mem. Cognit. 7, 476-484. 1979b. 25. MILNEK, B. Visual recognition and recall after right temporal lobe excision in man. Nruropsycholoyia 6,

191 201. 1968. 26. Mok NT(‘ASTI.F. V. B. Brain mechanisms for directed attention. J. Roy. SK. Med. 71, l4- 28, 1978. 27. NAVON. D. Forest before trees: the precedence of global features in visual perception. Cognit. Psycho/. 9,

353 3x3. 1977. 28. POHL. W. Dissociation of spatial discrimination deficits following frontal and parietal lesions in monkey. .I.

corn,,. pl~wiol. P.~~cho/. 82, :27--239, 1973.

ATTENTION AND INTERFERENCE 483

29. POMERANTZ, J. R. Global and local precedence: selective attention in form and motion perception. J. r\-p. Psychol.: Gen. 112, 516540, 1983.

30. POSNER, M. I., WALKER, J. A., FRIEDRICH, F. J. and RAFAL, R. D. Effects ofparietal injury on covert orienting of attention. J. Neurosci. 4, 1863-1874, 1984.

3 I. RATCLIFF, G. and DAVIES-JONES, A. B. Defective visual localization in focal brain wounds. Bruin 9549 60,1972. 32. RATCLIFF, G. and NEWCOMBE, F. Spatial orientation in man: effects of left. right and bilateral posterior cerebral

lesions. J. New-d. Neurosurg. Psych&. 36, 448454, 1973. 33. ROBERTSON, L. C. and DELIS, D. C. “Part-whole” processing in unilateral brain damaged patients: dysfunction

of hierarchical organization. Neuropsycholoyia 24, 363-370, 1986. 34. ROBERTSON, L. C., LAMB, M. R. and KNIGHT, R. T. Effects oflesions of temporal-parietal junction on perceptual

and attentional processing in humans. J. Neurosci., in press. 35. SELTZER, B. and PANDYA, D. N. Further observations on parieto-temporal connections in the rhesus monkey.

Expl Brain Res. 55, 301-312, 1984. 36. SERGENT, J. The cerebral balance of power: confrontation or cooperation‘? J. exp. P.sycho/.: Hum. Percept.

Perform. 8, 253-272, 1982. 37. UNGERLEIVER, L. G. and DESIMONE, R. Cortical connections of visual area MT in the macaque. J. camp. Neural.

248, 19&222, 1986. 38. UNGERLEIVER, L. G. and MISHKIN, M. Two cortical visual systems. In Analysis qf Visual Behavior, D. J. IKSLE.

M. A. GOODALE and R. J. W. MANSFIELD (Editors). MIT Press, Cambridge, Massachusetts, 1982. 39. WUR~Z, R. H., GOLDBERG, M. E. and ROBINSON, D. L. Behavioral modulation of visual responses in the

monkey: stimulus selection for attention and movement. Prog. Psych&d. Physiol. Psycho/. 9, 43 83, 1980.