Sensorimotor Disturbances in Patients With Lesions of the Parietal Cortex

Abstract

Somatosensory and motor disturbances of hand function were examined in 9 patients with parietal lobe lesions. A quantitative score was used for the elaboration of sensorimotor profiles displaying the relative degree of functional impairment. In patients with anterior parietal lobe lesions somaesthesis was clearly more disturbed than motor function. Simple aspects of somaesthesis (surface sensibility, two-point discrimination, position sense) were disturbed to about the same degree as complex somatosensory (tactile recognition) tasks. On the other hand, patients with lesions of the posterior parietal lobe showed preferential impairment of complex somatosensory and motor functions (exploratory and manipulative finger movements). In 4 patients, analysis of motor behaviour by means of an optoelectronic system showed that reaching, formation of hand aperture and target acquisition were less disturbed than manipulative behaviour. Finger movement trajectories during dynamic digital palpation of objects were grossly deranged in the patients with posterior parietal damage. The temporal characteristics of the finger movements during active touch were completely destroyed. This leads to a breakdown of the finely tuned digital scanning process required for the sequential sampling of mechanoreceptive information. Remarkably, these patients could produce the exploratory finger movements imitatively. The motor disability of the parietal hand does not lie in the loss of the kinetic memory to perform these movements, but in the loss of their evocation by appropriate sensory stimuli. This deficit is not due to a lack of somatosensory information because that may be relatively well preserved. It is concluded that the motor disturbance in posterior parietal lobe disease lies essentially in the conception and execution of the spatiotemporal movement patterns necessary to bring those receptors into action which would normally provide the information about tactile objects. This illustrates the intricate mutual dependence of the spatiotemporal organization of receptor activation by movement and of the formation of movement trajectories on the basis of adequate sensory processing.

Action observation activates premotor and parietal areas in a somatotopic manner: an fMRI study

“…In the monkey, mouth movements are represented in the rostral part of PF (Leinonen & Nyman, 1979;Fogassi et al, 1998), distal hand movements in the anterior intraparietal area and arm reaching movements, posteriorly on the medial bank of the intraparietal sulcus (Colby & Duhamel, 1991;Snyder et al, 1997). Furthermore, clinical and brain imaging studies strongly suggest that a segregated pattern of effector representations in the parietal lobe is also present in humans (De Renzi, 1982;Jeannerod, 1986;Pause et al, 1989;Seitz et al, 1991).…”

Enhanced Accuracy in Novel Mirror Drawing after Repetitive Transcranial Magnetic Stimulation-Induced Proprioceptive Deafferentation

“…Patients with a decrease in proprioception have great difficulties with controlling their hand (Rothwell et al, 1982;Jeannerod et al, 1984;Sanes et al, 1985;Pause et al, 1989). Visual feedback, however, improves the accuracy of their movements (Ghez et al, 1995), reducing (Sanes et al, 1984) or even eliminating (Bard et al, 1995) the difference in performance between patients and healthy controls.…”

“…rTMS at 1 Hz reduces cortical excitability, producing a so-called "virtual lesion" (PascualLeone et al, 1999;Siebner and Rothwell, 2003). In neurological patients, a lesion of the anterior parietal cortex impairs the sense of position of the contralateral arm (Corkin et al, 1970) but spares the ability to perform voluntary movements (Pause et al, 1989). Here, we show that rTMS applied at an anterior parietal site improved trajectory accuracy during a novel mirror drawing task performed with the contralateral hand.…”

Episodic retrieval and the cortical binding of relational activity

“…Patients with PPC lesions exhibit a variety of cognitive disorders, including deficits in visuospatial attention, sensorimotor integration, and verbal short-term memory (see Baldo & Dronkers, 2006;Egly, Driver, & Rafal, 1994;Olson & Berryhill, 2009;Pause, Kunesch, Binkofski, & Freund, 1989;Warrington & Shallice, 1969). Such patients do not exhibit severe impairment in learning and memory, certainly not to the same degree as patients with MTL or PFC lesions.…”